// Slower C++ solution:
#define _USE_MATH_DEFINES

#include <cstdio>

#include <iostream>

#include <sstream>

#include <fstream>

#include <iomanip>

#include <algorithm>

#include <cmath>

#include <complex>

#include <string>

#include <vector>

#include <list>

#include <queue>

#include <stack>

#include <set>

#include <map>

#include <bitset>

#include <numeric>

#include <limits>

#include <climits>

#include <cfloat>

#include <functional>

#include <iterator>

using namespace std;



void stronglyConnectedComponents(const vector<vector<int> >& edges, vector<int>& indexConvert,

                                 vector<vector<int> >& nodesOut, vector<vector<int> >& edgesOut)

{

    const int n = edges.size();

    vector<int> num(n, -1), low(n, -1);

    vector<bool> isStk(n, false);

    stack<int> stk;

    int cnt = -1;

    nodesOut.clear();



    for(int i=0; i<n; ++i){

        stack<pair<int, unsigned> > arg;

        arg.push(make_pair(i, 0));



        while(!arg.empty()){

            int v = arg.top().first;

            unsigned j = arg.top().second;

            arg.pop();



            if(j == 0){

                if(num[v] != -1)

                    continue;

                num[v] = low[v] = ++ cnt;

                stk.push(v);

                isStk[v] = true;

            }

            else{

                int w = edges[v][j-1];

                if(isStk[w])

                    low[v] = min(low[v], low[w]);

            }



            if(j < edges[v].size()){

                arg.push(make_pair(v, j + 1));

                int w = edges[v][j];

                arg.push(make_pair(w, 0));

            }

            else if(low[v] == num[v]){

                nodesOut.push_back(vector<int>());

                for(;;){

                    int w = stk.top();

                    stk.pop();

                    isStk[w] = false;

                    nodesOut.back().push_back(w);

                    if(v == w)

                        break;

                }

            }

        }

    }



    reverse(nodesOut.begin(), nodesOut.end()); // DAGにするために反転させる

    const int m = nodesOut.size();

    indexConvert.resize(n);

    for(int i=0; i<m; ++i){

        for(unsigned j=0; j<nodesOut[i].size(); ++j)

            indexConvert[nodesOut[i][j]] = i;

    }

    edgesOut.assign(m, vector<int>());

    vector<set<int> > used(m);

    for(int i=0; i<n; ++i){

        for(unsigned j=0; j<edges[i].size(); ++j){

            int v = indexConvert[i];

            int w = indexConvert[edges[i][j]];

            if(v != w && used[v].find(w) == used[v].end()){

                edgesOut[v].push_back(w);

                used[v].insert(w);

            }

        }

    }

}



bool is2sat(int n, const vector<pair<int, bool> >& cs, vector<bool>& ans)

{

    vector<vector<int> > edges1(2*n);

    for(unsigned i=0; i<cs.size(); i+=2){

        int a = cs[i].first * 2 + (cs[i].second ? 0 : 1);

        int b = cs[i+1].first * 2 + (cs[i+1].second ? 0 : 1);

        edges1[a^1].push_back(b);

        edges1[b^1].push_back(a);

    }



    vector<int> indexConvert;

    vector<vector<int> > nodes, edges2;

    stronglyConnectedComponents(edges1, indexConvert, nodes, edges2);



    ans.resize(n);

    for(int i=0; i<n; ++i){

        if(indexConvert[2*i] < indexConvert[2*i+1])

            ans[i] = false;

        else if(indexConvert[2*i+1] < indexConvert[2*i])

            ans[i] = true;

        else

            return false;

    }

    return true;

}



class SegmentTree

{

private:

    int n;

    void getRangeIndex(int a, int b, int k, int l, int r, vector<int>& index){

        if(a <= l && r <= b){

            index.push_back(k);

        }

        else if(a <= r && l <= b){

            getRangeIndex(a, b, k*2+1, l, (l+r)/2, index);

            getRangeIndex(a, b, k*2+2, (l+r+1)/2, r, index);

        }

    }

public:

    SegmentTree(int n0){

        n = 1;

        while(n < n0)

            n *= 2;

    }

    int getNodeNum(){

        return 2 * n - 1;

    }

    int getLeafIndex(int a){

        return n - 1 + a;

    }

    int getParentIndex(int a){

        if(a == 0)

            return -1;

        else

            return (a - 1) / 2;

    }

    void getRangeIndex(int a, int b, vector<int>& index){

        index.clear();

        return getRangeIndex(a, b, 0, 0, n-1, index);

    }

};



int main()

{

    int n;

    cin >> n;

    vector<pair<int, int> > flag(2*n);

    for(int i=0; i<2*n; ++i){

        cin >> flag[i].first;

        flag[i].second = i;

    }



    sort(flag.begin(), flag.end());

    vector<int> index(2*n);

    for(int i=0; i<2*n; ++i)

        index[flag[i].second] = i;



    SegmentTree st(2*n);

    int m = st.getNodeNum();



    int left = 0;

    int right = 1000000000;

    while(left < right){

        vector<pair<int, bool> > cs;

        for(int a=1; a<m; ++a){

            int b = st.getParentIndex(a);

            cs.push_back(make_pair(a, false));

            cs.push_back(make_pair(b, true));

        }

        for(int i=0; i<n; ++i){

            cs.push_back(make_pair(st.getLeafIndex(index[2*i]), true));

            cs.push_back(make_pair(st.getLeafIndex(index[2*i+1]), true));

        }



        int mid = (left + right + 1) / 2;

        int j = 0;

        int k = 0;

        for(int i=0; i<2*n; ++i){

            while(flag[i].first - flag[j].first >= mid)

                ++ j;

            while(k < 2*n && flag[k].first - flag[i].first < mid)

                ++ k;



            vector<int> v;

            st.getRangeIndex(j, i-1, v);

            for(int a : v){

                cs.push_back(make_pair(st.getLeafIndex(i), false));

                cs.push_back(make_pair(a, false));

            }

            st.getRangeIndex(i+1, k-1, v);

            for(int a : v){

                cs.push_back(make_pair(st.getLeafIndex(i), false));

                cs.push_back(make_pair(a, false));

            }

        }



        vector<bool> tmp;

        if(is2sat(m, cs, tmp))

            left = mid;

        else

            right = mid - 1;

    }



    cout << left << endl;



    return 0;

}


// Faster C++ solution for the same problem (measured speedup: 1.3655097112529648x):
#define _USE_MATH_DEFINES

#include <cstdio>

#include <iostream>

#include <sstream>

#include <fstream>

#include <iomanip>

#include <algorithm>

#include <cmath>

#include <complex>

#include <string>

#include <vector>

#include <list>

#include <queue>

#include <stack>

#include <set>

#include <map>

#include <bitset>

#include <numeric>

#include <limits>

#include <climits>

#include <cfloat>

#include <functional>

#include <iterator>

using namespace std;



void stronglyConnectedComponents(const vector<vector<int> >& edges, vector<int>& indexConvert,

                                 vector<vector<int> >& nodesOut)

{

    const int n = edges.size();

    vector<int> num(n, -1), low(n, -1);

    vector<bool> isStk(n, false);

    stack<int> stk;

    int cnt = -1;

    nodesOut.clear();



    for(int i=0; i<n; ++i){

        stack<pair<int, unsigned> > arg;

        arg.push(make_pair(i, 0));



        while(!arg.empty()){

            int v = arg.top().first;

            unsigned j = arg.top().second;

            arg.pop();



            if(j == 0){

                if(num[v] != -1)

                    continue;

                num[v] = low[v] = ++ cnt;

                stk.push(v);

                isStk[v] = true;

            }

            else{

                int w = edges[v][j-1];

                if(isStk[w])

                    low[v] = min(low[v], low[w]);

            }



            if(j < edges[v].size()){

                arg.push(make_pair(v, j + 1));

                int w = edges[v][j];

                arg.push(make_pair(w, 0));

            }

            else if(low[v] == num[v]){

                nodesOut.push_back(vector<int>());

                for(;;){

                    int w = stk.top();

                    stk.pop();

                    isStk[w] = false;

                    nodesOut.back().push_back(w);

                    if(v == w)

                        break;

                }

            }

        }

    }



    reverse(nodesOut.begin(), nodesOut.end()); // DAGにするために反転させる

    const int m = nodesOut.size();

    indexConvert.resize(n);

    for(int i=0; i<m; ++i){

        for(unsigned j=0; j<nodesOut[i].size(); ++j)

            indexConvert[nodesOut[i][j]] = i;

    }

}



bool is2sat(int n, const vector<pair<int, bool> >& cs, vector<bool>& ans)

{

    vector<vector<int> > edges1(2*n);

    for(unsigned i=0; i<cs.size(); i+=2){

        int a = cs[i].first * 2 + (cs[i].second ? 0 : 1);

        int b = cs[i+1].first * 2 + (cs[i+1].second ? 0 : 1);

        edges1[a^1].push_back(b);

        edges1[b^1].push_back(a);

    }



    vector<int> indexConvert;

    vector<vector<int> > nodes;

    stronglyConnectedComponents(edges1, indexConvert, nodes);



    ans.resize(n);

    for(int i=0; i<n; ++i){

        if(indexConvert[2*i] < indexConvert[2*i+1])

            ans[i] = false;

        else if(indexConvert[2*i+1] < indexConvert[2*i])

            ans[i] = true;

        else

            return false;

    }

    return true;

}



class SegmentTree

{

private:

    int n;

    void getRangeIndex(int a, int b, int k, int l, int r, vector<int>& index){

        if(a <= l && r <= b){

            index.push_back(k);

        }

        else if(a <= r && l <= b){

            getRangeIndex(a, b, k*2+1, l, (l+r)/2, index);

            getRangeIndex(a, b, k*2+2, (l+r+1)/2, r, index);

        }

    }

public:

    SegmentTree(int n0){

        n = 1;

        while(n < n0)

            n *= 2;

    }

    int getNodeNum(){

        return 2 * n - 1;

    }

    int getLeafIndex(int a){

        return n - 1 + a;

    }

    int getParentIndex(int a){

        if(a == 0)

            return -1;

        else

            return (a - 1) / 2;

    }

    void getRangeIndex(int a, int b, vector<int>& index){

        index.clear();

        return getRangeIndex(a, b, 0, 0, n-1, index);

    }

};



int main()

{

    int n;

    cin >> n;

    vector<pair<int, int> > flag(2*n);

    for(int i=0; i<2*n; ++i){

        cin >> flag[i].first;

        flag[i].second = i;

    }



    sort(flag.begin(), flag.end());

    vector<int> index(2*n);

    for(int i=0; i<2*n; ++i)

        index[flag[i].second] = i;



    SegmentTree st(2*n);

    int m = st.getNodeNum();



    int left = 0;

    int right = 1000000000;

    while(left < right){

        vector<pair<int, bool> > cs;

        for(int a=1; a<m; ++a){

            int b = st.getParentIndex(a);

            cs.push_back(make_pair(a, false));

            cs.push_back(make_pair(b, true));

        }

        for(int i=0; i<n; ++i){

            cs.push_back(make_pair(st.getLeafIndex(index[2*i]), true));

            cs.push_back(make_pair(st.getLeafIndex(index[2*i+1]), true));

        }



        int mid = (left + right + 1) / 2;

        int j = 0;

        for(int i=0; i<2*n; ++i){

            while(flag[i].first - flag[j].first >= mid)

                ++ j;



            vector<int> v;

            st.getRangeIndex(j, i-1, v);

            for(int a : v){

                cs.push_back(make_pair(st.getLeafIndex(i), false));

                cs.push_back(make_pair(a, false));

            }

        }



        vector<bool> tmp;

        if(is2sat(m, cs, tmp))

            left = mid;

        else

            right = mid - 1;

    }



    cout << left << endl;



    return 0;

}