import java.io.*;
import java.math.*;
import java.util.*;
import java.util.Map.Entry;
import static java.util.Arrays.*;
public class Main {
private static final int mod = (int)1e9+7;
final Random random = new Random(0);
final IOFast io = new IOFast();
/// MAIN CODE
public void run() throws IOException {
// int TEST_CASE = Integer.parseInt(new String(io.nextLine()).trim());
int TEST_CASE = 1;
while(TEST_CASE-- != 0) {
int n = io.nextInt();
int[] x = new int[n];
int[] y = new int[n];
int[][] pos = new int[n*2][];
for (int i = 0; i < n; i++) {
x[i] = io.nextInt();
y[i] = io.nextInt();
// x[i] = random.nextInt((int)1e9)+1;
// y[i] = random.nextInt((int)1e9)+1;
pos[2*i+0] = new int[]{x[i], 2*i+0};
pos[2*i+1] = new int[]{y[i], 2*i+1};
}
Arrays.sort(pos, (a,b)->a[0]-b[0]);
int[] idx = new int[2*n];
int[] pos2 = new int[n*2];
for (int i = 0; i < 2*n; i++) {
idx[pos[i][1]] = i;
pos2[i] = pos[i][0];
}
int times = 0;
int m = Integer.highestOneBit(pos.length) << 1;
sat = new Sat2(2*m-1);
int low = 0, high = (int)1e9;
while (high - low > 1) {
int mid = (low + high) / 2;
sat.clear();
if (times++ == 16) System.gc();
for (int i = 0; i < m - 1; i++) {
for (int j = 1; j <= 2; j++) {
final int c = 2*i+j;
// 親が偽 => 子が偽
// A => B, not(A) v B
// not(p) => not(c)
// p v not(c)
// sat.Or(i, sat.Not(c));
// sat.Or(sat.Not(c), i);
sat.Implication(sat.Not(i), sat.Not(c));
}
}
for (int i = 0; i < idx.length; i += 2) {
// x[i], y[i]のどちらか一方しか使用できない
sat.Or(idx[i+0] + m - 1, idx[i+1] + m - 1);
sat.Or(sat.Not(idx[i+0] + m - 1), sat.Not(idx[i+1] + m - 1));
}
for (int i = 0; i < pos.length; i++) {
int j = lowerBound(pos2, pos2[i] - mid + 1);
int k = upperBound(pos2, pos2[i] + mid - 1);
addEdge(j, i, 0, m, 0, i+m-1);
addEdge(i+1, k, 0, m, 0, i+m-1);
}
if (sat.satisfy()) low = mid;
else high = mid;
}
io.out.println(low);
}
}
Sat2 sat;
void addEdge(int l, int r, int curL, int curR, int k, int i) {
if (l >= curR || r <= curL) return;
if (l <= curL && curR <= r) {
// i => not(k)
// sat.Or(sat.Not(i), sat.Not(k));
sat.Implication(i, sat.Not(k));
return;
}
final int curM = (curL + curR) / 2;
addEdge(l, r, curL, curM, 2*k+1, i);
addEdge(l, r, curM, curR, 2*k+2, i);
}
int lowerBound(int[] xs, int key) {
int low = -1, high = xs.length;
while (high - low > 1) {
int mid = (low + high) / 2;
if (xs[mid] >= key) high = mid;
else low = mid;
}
return low + 1;
}
int upperBound(int[] xs, int key) {
return lowerBound(xs, key + 1);
}
static public class Sat2 {
final int n;
final boolean[] ans;
final StronglyConnectedComponent scc;
void clear() {
scc.clear();
}
public void Implication(int a, int b) {
scc.addEdge(a, b);
}
public Sat2(int n) {
this.n = n;
ans = new boolean[n];
scc = new StronglyConnectedComponent(n * 2);
}
private int Not(int a) {
if(a < 0 || a >= 2 * n) throw new RuntimeException();
return a >= n ? a - n : a + n;
}
public void Or(int a, int b) {
if(a < 0 || a >= 2 * n || b < 0 || b >= 2 * n) throw new RuntimeException();
scc.addEdge(Not(a), b);
scc.addEdge(Not(b), a);
}
public boolean satisfy() {
scc.scc();
for(int i = 0; i < n; i++) {
// 同じ強連結成分に含まれたら充足不可能
if(scc.cmp[i] == scc.cmp[i + n]) {
return false;
}
}
for(int i = 0; i < n; i++) {
ans[i] = scc.cmp[i] > scc.cmp[i + n];
}
return true;
}
static public class StronglyConnectedComponent {
int V;
List<List<Integer>> G;
List<List<Integer>> rG;
List<Integer> vs;
boolean[] used;
public int[] cmp;
void clear() {
for (int i = 0; i < V; i++) {
G.get(i).clear();
rG.get(i).clear();
}
}
public StronglyConnectedComponent(int n) {
V = n;
G = new ArrayList<List<Integer>>(n);
rG = new ArrayList<List<Integer>>(n);
vs = new ArrayList<Integer>();
used = new boolean[n];
cmp = new int[n];
for (int i = 0; i < n; i++) {
G.add(new ArrayList<Integer>());
rG.add(new ArrayList<Integer>());
}
}
public void addEdge(int from, int to) {
G.get(from).add(to);
rG.get(to).add(from);
}
private void dfs(int v) {
used[v] = true;
for (int i = 0; i < G.get(v).size(); i++)
if (!used[G.get(v).get(i)])
dfs(G.get(v).get(i));
vs.add(v);
}
private void rdfs(int v, int k) {
used[v] = true;
cmp[v] = k;
for (int i = 0; i < rG.get(v).size(); i++)
if (!used[rG.get(v).get(i)])
rdfs(rG.get(v).get(i), k);
}
public int scc() {
for (int i = 0; i < V; i++)
used[i] = false;
vs.clear();
for (int i = 0; i < V; i++)
if (!used[i])
dfs(i);
for (int i = 0; i < V; i++)
used[i] = false;
int k = 0;
for (int i = vs.size() - 1; i >= 0; i--)
if (!used[vs.get(i)])
rdfs(vs.get(i), k++);
return k;
}
}
}
static public class Sat2_2 {
final int n;
final boolean[] ans;
final StronglyConnectedComponent scc;
void clear() {
scc.clear();
}
public Sat2_2(int n) {
this.n = n;
ans = new boolean[n];
scc = new StronglyConnectedComponent(n * 2);
}
private int Not(int a) {
if(a < 0 || a >= 2 * n) throw new RuntimeException();
return a >= n ? a - n : a + n;
}
public void Or(int a, int b) {
if(a < 0 || a >= 2 * n || b < 0 || b >= 2 * n) throw new RuntimeException();
scc.addEdge(Not(a), b);
scc.addEdge(Not(b), a);
}
public boolean satisfy() {
scc.scc();
for(int i = 0; i < n; i++) {
// 同じ強連結成分に含まれたら充足不可能
if(scc.cmp[i] == scc.cmp[i + n]) {
return false;
}
}
for(int i = 0; i < n; i++) {
ans[i] = scc.cmp[i] > scc.cmp[i + n];
}
return true;
}
static class SimpleAdjListGraph {
int m, V, E;
int[] head, next, to;
public SimpleAdjListGraph(int V, int E) {
head = new int[V];
next = new int[E];
to = new int[E];
this.V = V;
this.E = E;
clear();
}
public void clear() {
m = 0;
Arrays.fill(head, -1);
}
public void addEdge(int s, int t) {
next[m] = head[s];
head[s] = m;
to[m++] = t;
}
}
static public class StronglyConnectedComponent {
int V;
SimpleAdjListGraph G;
SimpleAdjListGraph rG;
int len;
int[] vs;
boolean[] used;
public int[] cmp;
void clear() {
G.clear();
rG.clear();
}
public StronglyConnectedComponent(int n) {
V = n;
G = new SimpleAdjListGraph(n, Math.min(10000*10000/5, n*n));
rG = new SimpleAdjListGraph(n, Math.min(10000*10000/5, n*n));
vs = new int[n*2];
used = new boolean[n];
cmp = new int[n];
}
public void addEdge(int from, int to) {
G.addEdge(from, to);
rG.addEdge(to, from);
}
private void dfs(int v) {
used[v] = true;
for (int e = G.head[v]; e != -1; e = G.next[e])
if (!used[G.to[e]])
dfs(G.to[e]);
vs[len++] = v;
}
private void rdfs(int v, int k) {
used[v] = true;
cmp[v] = k;
for (int e = rG.head[v]; e != -1; e = rG.next[e])
if (!used[rG.to[e]])
rdfs(rG.to[e], k);
}
public int scc() {
for (int i = 0; i < V; i++)
used[i] = false;
len = 0;
for (int i = 0; i < V; i++)
if (!used[i])
dfs(i);
for (int i = 0; i < V; i++)
used[i] = false;
int k = 0;
for (int i = len - 1; i >= 0; i--)
if (!used[vs[i]])
rdfs(vs[i], k++);
return k;
}
}
}
/// TEMPLATE
static int gcd(int n, int r) { return r == 0 ? n : gcd(r, n%r); }
static long gcd(long n, long r) { return r == 0 ? n : gcd(r, n%r); }
static <T> void swap(T[] x, int i, int j) { T t = x[i]; x[i] = x[j]; x[j] = t; }
static void swap(int[] x, int i, int j) { int t = x[i]; x[i] = x[j]; x[j] = t; }
void printArrayLn(int[] xs) { for(int i = 0; i < xs.length; i++) io.out.print(xs[i] + (i==xs.length-1?"\n":" ")); }
void printArrayLn(long[] xs) { for(int i = 0; i < xs.length; i++) io.out.print(xs[i] + (i==xs.length-1?"\n":" ")); }
static void dump(Object... o) { System.err.println(Arrays.deepToString(o)); }
void main() throws IOException {
// IOFast.setFileIO("rle-size.in", "rle-size.out");
try { run(); }
catch (EndOfFileRuntimeException e) { }
io.out.flush();
}
public static void main(String[] args) throws IOException { new Main().main(); }
static class EndOfFileRuntimeException extends RuntimeException {
private static final long serialVersionUID = -8565341110209207657L; }
static
public class IOFast {
private BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
private PrintWriter out = new PrintWriter(System.out);
void setFileIn(String ins) throws IOException { in.close(); in = new BufferedReader(new FileReader(ins)); }
void setFileOut(String outs) throws IOException { out.flush(); out.close(); out = new PrintWriter(new FileWriter(outs)); }
void setFileIO(String ins, String outs) throws IOException { setFileIn(ins); setFileOut(outs); }
private static int pos, readLen;
private static final char[] buffer = new char[1024 * 8];
private static char[] str = new char[500*8*2];
private static boolean[] isDigit = new boolean[256];
private static boolean[] isSpace = new boolean[256];
private static boolean[] isLineSep = new boolean[256];
static { for(int i = 0; i < 10; i++) { isDigit['0' + i] = true; } isDigit['-'] = true; isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true; isLineSep['\r'] = isLineSep['\n'] = true; }
public int read() throws IOException { if(pos >= readLen) { pos = 0; readLen = in.read(buffer); if(readLen <= 0) { throw new EndOfFileRuntimeException(); } } return buffer[pos++]; }
public int nextInt() throws IOException { int len = 0; str[len++] = nextChar(); len = reads(len, isSpace); int i = 0; int ret = 0; if(str[0] == '-') { i = 1; } for(; i < len; i++) ret = ret * 10 + str[i] - '0'; if(str[0] == '-') { ret = -ret; } return ret; }
public long nextLong() throws IOException { int len = 0; str[len++] = nextChar(); len = reads(len, isSpace); int i = 0; long ret = 0; if(str[0] == '-') { i = 1; } for(; i < len; i++) ret = ret * 10 + str[i] - '0'; if(str[0] == '-') { ret = -ret; } return ret; }
public char nextChar() throws IOException { while(true) { final int c = read(); if(!isSpace[c]) { return (char)c; } } }
int reads(int len, boolean[] accept) throws IOException { try { while(true) { final int c = read(); if(accept[c]) { break; } if(str.length == len) { char[] rep = new char[str.length * 3 / 2]; System.arraycopy(str, 0, rep, 0, str.length); str = rep; } str[len++] = (char)c; } } catch(EndOfFileRuntimeException e) { ; } return len; }
int reads(char[] cs, int len, boolean[] accept) throws IOException { try { while(true) { final int c = read(); if(accept[c]) { break; } cs[len++] = (char)c; } } catch(EndOfFileRuntimeException e) { ; } return len; }
public char[] nextLine() throws IOException { int len = 0; str[len++] = nextChar(); len = reads(len, isLineSep); try { if(str[len-1] == '\r') { len--; read(); } } catch(EndOfFileRuntimeException e) { ; } return Arrays.copyOf(str, len); }
public String nextString() throws IOException { return new String(next()); }
public char[] next() throws IOException { int len = 0; str[len++] = nextChar(); len = reads(len, isSpace); return Arrays.copyOf(str, len); }
// public int next(char[] cs) throws IOException { int len = 0; cs[len++] = nextChar(); len = reads(cs, len, isSpace); return len; }
public double nextDouble() throws IOException { return Double.parseDouble(nextString()); }
public long[] nextLongArray(final int n) throws IOException { final long[] res = new long[n]; for(int i = 0; i < n; i++) { res[i] = nextLong(); } return res; }
public int[] nextIntArray(final int n) throws IOException { final int[] res = new int[n]; for(int i = 0; i < n; i++) { res[i] = nextInt(); } return res; }
public int[][] nextIntArray2D(final int n, final int k) throws IOException { final int[][] res = new int[n][]; for(int i = 0; i < n; i++) { res[i] = nextIntArray(k); } return res; }
public int[][] nextIntArray2DWithIndex(final int n, final int k) throws IOException { final int[][] res = new int[n][k+1]; for(int i = 0; i < n; i++) { for(int j = 0; j < k; j++) { res[i][j] = nextInt(); } res[i][k] = i; } return res; }
public double[] nextDoubleArray(final int n) throws IOException { final double[] res = new double[n]; for(int i = 0; i < n; i++) { res[i] = nextDouble(); } return res; }
}
}