// Slower C++ solution:
#include <algorithm>

#include <cassert>

#include <iostream>

#include <vector>

using namespace std;



struct two_sat {

    int n = 0;

    vector<vector<int>> adj;

    vector<bool> assignment;



    int inv(int var) {

        return var ^ 1;

    }



    int new_var() {

        adj.emplace_back();

        adj.emplace_back();

        return 2 * n++;

    }



    void implies(int a, int b) {

        adj[a].push_back(b);

        adj[inv(b)].push_back(inv(a));

    }



    void either(int a, int b) {

        adj[inv(a)].push_back(b);

        adj[inv(b)].push_back(a);

    }



    void set_value(int a) {

        adj[inv(a)].push_back(a);

    }



    void equal(int a, int b) {

        implies(a, b);

        implies(inv(a), inv(b));

    }



    void unequal(int a, int b) {

        implies(a, inv(b));

        implies(inv(a), b);

    }



    // Warning: this only creates an implication in the negative direction. It is still possible for

    // a = b = true with and_var = false. In particular, it does not work to call set_value on inv(and_var).

    int create_and(int a, int b) {

        if (a < 0 || b < 0) return max(a, b);

        int result = new_var();

        implies(result, a);

        implies(result, b);

        return result;

    }



    // Warning: this only creates an implication in the positive direction. It is still possible for

    // a = b = false with or_var = true. In particular, it does not work to call set_value on or_var.

    int create_or(int a, int b) {

        if (a < 0 || b < 0) return max(a, b);

        int result = new_var();

        implies(a, result);

        implies(b, result);

        return result;

    }



    int create_at_most_one(int a, int b) {

        if (a < 0 || b < 0) return max(a, b);

        either(inv(a), inv(b));

        return create_or(a, b);

    }



    template<typename T_iterable>

    int create_at_most_one(const T_iterable &vars) {

        int aux = -1;



        for (int var : vars)

            aux = create_at_most_one(aux, var);



        return aux;

    }



    bool solve() {

        assignment.assign(2 * n, false);

        vector<bool> vis[2];

        vector<int> q[2];

        vis[0].assign(2 * n, false);

        vis[1].assign(2 * n, false);

        q[0].resize(2 * n);

        q[1].resize(2 * n);



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

            if (!assignment[2 * i] && !assignment[2 * i + 1]) {

                // we have to do the search

                bool bad[2] = {false, false};

                int qs[2] = {0, 0};

                int qi[2] = {0, 0};

                int qt[2] = {0, 0};



                for (int z = 0; z < 2; z++) {

                    vis[z][2 * i + z] = true;

                    q[z][qt[z]++] = 2 * i + z;

                }



                while (true) {

                    if (bad[0] && bad[1])

                        return false;



                    for (int z = 0; z < 2; z++) {

                        if (bad[z])

                            continue;



                        if (qs[z] >= qt[z]) {

                            // we're done, so we should finalize it

                            for (int ind = 0; ind < qt[z]; ind++)

                                assignment[q[z][ind]] = true;



                            bad[!z] = true;

                            goto done;

                        }



                        int v = q[z][qs[z]];



                        if (qi[z] == int(adj[v].size())) {

                            qs[z]++;

                            qi[z] = 0;

                            continue;

                        }



                        int u = adj[v][qi[z]];

                        assert(!assignment[inv(u)]);



                        if (vis[z][inv(u)]) {

                            bad[z] = true;

                        } else if (!assignment[u] && !vis[z][u]) {

                            vis[z][u] = true;

                            q[z][qt[z]++] = u;

                        }



                        qi[z]++;

                    }

                }



done:

                assert(bad[0] ^ bad[1]);



                // reset vis

                for (int z = 0; z < 2; z++)

                    for (int ind = 0; ind < qt[z]; ind++)

                        vis[z][q[z][ind]] = false;

            }



            assert(assignment[2 * i] ^ assignment[2 * i + 1]);

        }



        return true;

    }

};





const int INF = 1e9 + 5;



int N, T;

vector<pair<int, int>> sorted;

two_sat solver;

vector<int> tree;



void build_tree() {

    T = 2 * N;

    tree.assign(2 * T, -1);



    for (int t = 1; t < 2 * T; t++)

        tree[t] = solver.new_var();



    for (int t = 2; t < 2 * T; t++)

        solver.implies(tree[t / 2], tree[t]);



    for (int t = 0; t < T; t++)

        solver.implies(tree[T + t], solver.inv(sorted[t].second));

}



void add_range(int from, int start, int end) {

    for (start += T, end += T; start < end; start /= 2, end /= 2) {

        if (start & 1)

            solver.implies(from, tree[start++]);



        if (end & 1)

            solver.implies(from, tree[--end]);

    }

}



bool possible(int d) {

    solver = two_sat();



    for (int i = 0; i < N; i++)

        solver.new_var();



    build_tree();



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

        int start = lower_bound(sorted.begin(), sorted.end(), make_pair(sorted[i].first - d + 1, 0)) - sorted.begin();

        int end = lower_bound(sorted.begin(), sorted.end(), make_pair(sorted[i].first + d, 0)) - sorted.begin();

        add_range(sorted[i].second, start, i);

        add_range(sorted[i].second, i + 1, end);

    }



    return solver.solve();

}



int main() {

    ios::sync_with_stdio(false);

    cin.tie(nullptr);



    cin >> N;



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

        int x, y;

        cin >> x >> y;

        sorted.emplace_back(x, 2 * i);

        sorted.emplace_back(y, 2 * i + 1);

    }



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

    int low = 0, high = INF;



    while (low < high) {

        int mid = (low + high + 1) / 2;



        if (possible(mid))

            low = mid;

        else

            high = mid - 1;

    }



    cout << low << '\n';

}


// Faster C++ solution for the same problem (measured speedup: 1.530653325855389x):
#include <algorithm>

#include <cassert>

#include <iostream>

#include <vector>

using namespace std;



struct two_sat {

    int n = 0;

    vector<vector<int>> adj;

    vector<bool> assignment;



    int inv(int var) {

        return var ^ 1;

    }



    int new_var() {

        adj.emplace_back();

        adj.emplace_back();

        return 2 * n++;

    }



    void implies(int a, int b) {

        adj[a].push_back(b);

        adj[inv(b)].push_back(inv(a));

    }



    void either(int a, int b) {

        adj[inv(a)].push_back(b);

        adj[inv(b)].push_back(a);

    }



    void set_value(int a) {

        adj[inv(a)].push_back(a);

    }



    void equal(int a, int b) {

        implies(a, b);

        implies(inv(a), inv(b));

    }



    void unequal(int a, int b) {

        implies(a, inv(b));

        implies(inv(a), b);

    }



    // Warning: this only creates an implication in the negative direction. It is still possible for

    // a = b = true with and_var = false. In particular, it does not work to call set_value on inv(and_var).

    int create_and(int a, int b) {

        if (a < 0 || b < 0) return max(a, b);

        int result = new_var();

        implies(result, a);

        implies(result, b);

        return result;

    }



    // Warning: this only creates an implication in the positive direction. It is still possible for

    // a = b = false with or_var = true. In particular, it does not work to call set_value on or_var.

    int create_or(int a, int b) {

        if (a < 0 || b < 0) return max(a, b);

        int result = new_var();

        implies(a, result);

        implies(b, result);

        return result;

    }



    int create_at_most_one(int a, int b) {

        if (a < 0 || b < 0) return max(a, b);

        either(inv(a), inv(b));

        return create_or(a, b);

    }



    template<typename T_iterable>

    int create_at_most_one(const T_iterable &vars) {

        int aux = -1;



        for (int var : vars)

            aux = create_at_most_one(aux, var);



        return aux;

    }



    bool solve() {

        assignment.assign(2 * n, false);

        vector<bool> vis[2];

        vector<int> q[2];

        vis[0].assign(2 * n, false);

        vis[1].assign(2 * n, false);

        q[0].resize(2 * n);

        q[1].resize(2 * n);



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

            if (!assignment[2 * i] && !assignment[2 * i + 1]) {

                // we have to do the search

                bool bad[2] = {false, false};

                int qs[2] = {0, 0};

                int qi[2] = {0, 0};

                int qt[2] = {0, 0};



                for (int z = 0; z < 2; z++) {

                    vis[z][2 * i + z] = true;

                    q[z][qt[z]++] = 2 * i + z;

                }



                while (true) {

                    if (bad[0] && bad[1])

                        return false;



                    for (int z = 0; z < 2; z++) {

                        if (bad[z])

                            continue;



                        if (qs[z] >= qt[z]) {

                            // we're done, so we should finalize it

                            for (int ind = 0; ind < qt[z]; ind++)

                                assignment[q[z][ind]] = true;



                            bad[!z] = true;

                            goto done;

                        }



                        int v = q[z][qs[z]];



                        if (qi[z] == int(adj[v].size())) {

                            qs[z]++;

                            qi[z] = 0;

                            continue;

                        }



                        int u = adj[v][qi[z]];

                        assert(!assignment[inv(u)]);



                        if (vis[z][inv(u)]) {

                            bad[z] = true;

                        } else if (!assignment[u] && !vis[z][u]) {

                            vis[z][u] = true;

                            q[z][qt[z]++] = u;

                        }



                        qi[z]++;

                    }

                }



done:

                assert(bad[0] ^ bad[1]);



                // reset vis

                for (int z = 0; z < 2; z++)

                    for (int ind = 0; ind < qt[z]; ind++)

                        vis[z][q[z][ind]] = false;

            }



            assert(assignment[2 * i] ^ assignment[2 * i + 1]);

        }



        return true;

    }

};





const int INF = 1e9 + 5;



int N, T;

vector<pair<int, int>> sorted;

two_sat solver;

vector<int> tree;



void build_tree() {

    T = 2 * N;

    tree.assign(2 * T, -1);



    for (int t = 1; t < 2 * T; t++)

        tree[t] = solver.new_var();



    for (int t = 2; t < 2 * T; t++)

        solver.implies(tree[t / 2], tree[t]);



    for (int t = 0; t < T; t++)

        solver.implies(tree[T + t], solver.inv(sorted[t].second));

}



void add_range(int from, int start, int end) {

    for (start += T, end += T; start < end; start /= 2, end /= 2) {

        if (start & 1)

            solver.implies(from, tree[start++]);



        if (end & 1)

            solver.implies(from, tree[--end]);

    }

}



bool possible(int d) {

    solver = two_sat();



    for (int i = 0; i < N; i++)

        solver.new_var();



    build_tree();



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

        int start = lower_bound(sorted.begin(), sorted.end(), make_pair(sorted[i].first - d + 1, 0)) - sorted.begin();

        int end = lower_bound(sorted.begin(), sorted.end(), make_pair(sorted[i].first + d, 0)) - sorted.begin();

        add_range(sorted[i].second, start, i);

        add_range(sorted[i].second, i + 1, end);

    }



    return solver.solve();

}



int main() {

    ios::sync_with_stdio(false);

    cin.tie(nullptr);



    cin >> N;



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

        int x, y;

        cin >> x >> y;

        sorted.emplace_back(x, 2 * i);

        sorted.emplace_back(y, 2 * i + 1);

    }



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

    int high = 1;



    while (possible(high))

        high *= 2;



    int low = high / 2;



    while (low < high) {

        int mid = (low + high + 1) / 2;



        if (possible(mid))

            low = mid;

        else

            high = mid - 1;

    }



    cout << low << '\n';

}