#include <iostream>
#include <cstdio>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>
#include <limits>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <bitset>
#include <unordered_map>
#include <unordered_set>
#define lowbit(x) ( x&(-x) )
#define pi 3.141592653589793
#define e 2.718281828459045
#define INF 0x3f3f3f3f
#define HalF (l + r)>>1
#define lsn rt<<1
#define rsn rt<<1|1
#define Lson lsn, l, mid
#define Rson rsn, mid+1, r
#define QL Lson, ql, qr
#define QR Rson, ql, qr
#define myself rt, l, r
#define pii pair<int, int>
#define MP(a, b) make_pair(a, b)
using namespace std;
typedef unsigned long long ull;
typedef unsigned int uit;
typedef long long ll;
const int maxN = 1e4 + 7;
int N, a[maxN][2], lsan[maxN << 1], _UP, l, r, lim, ans;
vector<int> same[maxN << 1];
namespace Graph
{
    const int maxP = (maxN << 3) + (maxN << 2);
    vector<int> E[maxP], NE[maxP];
    int root, tot, lc[maxP], rc[maxP];
    void build(int &rt, int fa, int l, int r)
    {
        rt = ++tot;
        if(fa) E[fa].push_back(rt);
        if(l == r) return;
        int mid = HalF;
        build(lc[rt], rt, l, mid);
        build(rc[rt], rt, mid + 1, r);
    }
    void Insert(int rt, int l, int r, int qx, int id)
    {
        if(l == r)
        {
            E[rt].push_back(id);
            return;
        }
        int mid = HalF;
        if(qx <= mid) Insert(lc[rt], l, mid, qx, id);
        else Insert(rc[rt], mid + 1, r, qx, id);
    }
    void update(int rt, int l, int r, int ql, int qr, int fid)
    {
        if(ql <= l && qr >= r)
        {
            NE[fid].push_back(rt);
            return;
        }
        int mid = HalF;
        if(qr <= mid) update(lc[rt], l, mid, ql, qr, fid);
        else if(ql > mid) update(rc[rt], mid + 1, r, ql, qr, fid);
        else { update(lc[rt], l, mid, ql, qr, fid); update(rc[rt], mid + 1, r, ql, qr, fid); }
    }
    int dfn[maxP], low[maxP], tim, Stap[maxP], Stop, Belong[maxP], Bcnt;
    bool instack[maxP];
    inline int another(int x) { return (x & 1) ? x + 1 : x - 1; }
    void Tarjan(int u)
    {
        dfn[u] = low[u] = ++tim;
        Stap[++Stop] = u;
        instack[u] = true;
        for(int v : E[u])
        {
            if(!dfn[v])
            {
                Tarjan(v);
                low[u] = min(low[u], low[v]);
            }
            else if(instack[v]) low[u] = min(low[u], dfn[v]);
        }
        for(int v : NE[u])
        {
            if(!dfn[v])
            {
                Tarjan(v);
                low[u] = min(low[u], low[v]);
            }
            else if(instack[v]) low[u] = min(low[u], dfn[v]);
        }
        if(u <= (N << 1))
        {
            int id = ceil(1. * u / 2), op = !(u & 1), val = a[id][op];
            for(int v : same[val])
            {
                if(another(v) == u) continue;
                if(!dfn[v])
                {
                    Tarjan(v);
                    low[u] = min(low[u], low[v]);
                }
                else if(instack[v]) low[u] = min(low[u], dfn[v]);
            }
        }
        if(dfn[u] == low[u])
        {
            Bcnt++;
            int v;
            do
            {
                v = Stap[Stop--];
                instack[v] = false;
                Belong[v] = Bcnt;
            } while(u ^ v);
        }
    }
    inline bool check()
    {
        for(int i=1; i<=tot; i++)
        {
            NE[i].clear();
            dfn[i] = 0;
            instack[i] = false;
        }
        for(int i=1, ql, qr; i<=N; i++)
        {
            ql = (int)(upper_bound(lsan + 1, lsan + _UP + 1, lsan[a[i][0]] - lim) - lsan);
            qr = (int)(lower_bound(lsan + 1, lsan + _UP + 1, lsan[a[i][0]] + lim) - lsan - 1);
            if(ql < a[i][0]) update(root, 1, _UP, ql, a[i][0] - 1, 2 * i - 1);
            if(qr > a[i][0]) update(root, 1, _UP, a[i][0] + 1, qr, 2 * i - 1);
            ql = (int)(upper_bound(lsan + 1, lsan + _UP + 1, lsan[a[i][1]] - lim) - lsan);
            qr = (int)(lower_bound(lsan + 1, lsan + _UP + 1, lsan[a[i][1]] + lim) - lsan - 1);
            if(ql < a[i][1]) update(root, 1, _UP, ql, a[i][1] - 1, 2 * i);
            if(qr > a[i][1]) update(root, 1, _UP, a[i][1] + 1, qr, 2 * i);
        }
        tim = Stop = Bcnt = 0;
        for(int i=1; i<=tot; i++) if(!dfn[i]) Tarjan(i);
        for(int i=1; i<=(N << 1); i += 2)
        {
            if(Belong[i] == Belong[i + 1]) return false;
        }
        return true;
    }
    void G_init()
    {
        root = 0;
        tot = N << 1;
        build(root, 0, 1, _UP);
        for(int i=1; i<=N; i++)
        {
            Insert(root, 1, _UP, a[i][0], 2 * i);
            Insert(root, 1, _UP, a[i][1], 2 * i - 1);
        }
    }
};
using namespace Graph;
int main()
{
    scanf("%d", &N);
    _UP = 0;
    for(int i=1; i<=N; i++) { scanf("%d%d", &a[i][0], &a[i][1]); lsan[++_UP] = a[i][0]; lsan[++_UP] = a[i][1]; }
    sort(lsan + 1, lsan + _UP + 1);
    _UP = (int)(unique(lsan + 1, lsan + _UP + 1) - lsan - 1);
    for(int i=1; i<=N; i++)
    {
        a[i][0] = (int)(lower_bound(lsan + 1, lsan + _UP + 1, a[i][0]) - lsan);
        same[a[i][0]].push_back(2 * i);
        a[i][1] = (int)(lower_bound(lsan + 1, lsan + _UP + 1, a[i][1]) - lsan);
        same[a[i][1]].push_back(2 * i - 1);
    }
    G_init();
    l = 1; r = 1e9;
    ans = 0;
    while(l <= r)
    {
        lim = HalF;
        if(check())
        {
            l = lim + 1;
            ans = lim;
        }
        else r = lim - 1;
    }
    printf("%d\n", ans);
    return 0;
}


Measured memory_bytes: 19724