//看看会不会爆int!数组会不会少了一维！

//取物问题一定要小心先手胜利的条件

#include <bits/stdc++.h>

using namespace std;

#pragma comment(linker,"/STACK:102400000,102400000")

#define LL long long

#define ALL(a) a.begin(), a.end()

#define pb push_back

#define mk make_pair

#define fi first

#define se second

#define haha printf("haha\n")

const int maxn =  + ;

struct TwoSAT{

    int n;

    vector<int> G[maxn];

    bool mark[maxn];

    int c, s[maxn];///c是表示目前dfs到的个数和已经被标记的集合s

    bool dfs(int x){

        if (mark[x ^ ]) return false;

        if (mark[x]) return true;

        mark[x] = true;

        s[c++] = x;

        for (int i = ; i < G[x].size(); i++)

            if (!dfs(G[x][i])) return false;

        return true;

    }

    void init(int n){

        this->n = n;

        for (int i = ; i <  * n; i++) G[i].clear();

        memset(mark, , sizeof(mark));

    }

    void add_edge(int x, int xval, int y, int yval){

        x = x *  + xval, y = y *  + yval;

        G[x ^ ].push_back(y);

        G[y ^ ].push_back(x);

    }

    bool solve(){

        for (int i = ; i <  * n; i += ){

            if (!mark[i] && !mark[i + ]){

                c = ;

                if (!dfs(i)){

                    while (c) mark[s[--c]] = false;

                    if (!dfs(i + )) return false;

                }

            }

        }

        return true;

    }

};

TwoSAT sat;

int n;

int E[maxn], L[maxn];

int ti[maxn][];

bool test(int p){

    sat.init(n);

    for (int i = ; i < n; i++){

        for (int x = ; x < ; x++){

            for (int j = i + ; j < n; j++){

                for (int y = ; y < ; y++){

                    if (abs(ti[i][x] - ti[j][y]) < p){

                        ///那就说明不成立，因此要建立成立的边

                        sat.add_edge(i, x ^ , j, y ^ );

                    }

                }

            }

        }

    }

    return sat.solve();

}

int main(){

    while (scanf("%d", &n) == ){

        int lb = , rb = ;

        for (int i = ; i < n; i++){

            scanf("%d%d", E + i, L + i);

            ti[i][] = E[i], ti[i][] = L[i];

            rb = max(rb, max(E[i], L[i]));

        }

        rb++;

        while (lb < rb - ){

            int mid = (lb + rb) / ;

            if (test(mid)) lb = mid;

            else rb = mid;

        }

        printf("%d\n",lb);

    }

    return ;

}