/// author: Mr.Hakimov

#include <bits/stdc++.h>
#include <chrono>

#define fi first
#define se second
#define pb push_back
#define pf push_front
#define Pb pop_back
#define Pf pop_front
#define all(x) (x).begin(), (x).end()
#define fin(s) freopen(s, "r", stdin);
#define fout(s) freopen(s, "w", stdout);

/* Just some advices:
1. If I use set/multiset, I will check it - is it correct to use set/multiset in a problem?
2. If I can't solve problem, I must write a program, which could help me to understand it much more better)
...
*/

using namespace std;

#pragma GCC optimize("Ofast")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

typedef long long LL;
typedef long double LD;

int TN = 1;
vector<vector<int>> g(1001, vector<int> (1001));
vector<vector<int>> revG(1001, vector<int> (1001));
bool usd[1001];
int n;

void dfs(int u, int m, vector<vector<int>> & g) {
    usd[u] = true;
    for (int i = 1; i <= n; ++i) {
        if (g[u][i] <= m && !usd[i]) {
            dfs(i, m, g);
        }
    }
}

bool can(int m) {
    for (int i = 1; i <= n; ++i) {
        usd[i] = false;
    }

    dfs(1, m, g);

    for (int i = 1; i <= n; ++i) {
        if (!usd[i]) {
            return false;
        }
    }

    for (int i = 1; i <= n; ++i) {
        usd[i] = false;
    }

    dfs(1, m, revG);

    for (int i = 1; i <= n; ++i) {
        if (!usd[i]) {
            return false;
        }
    }

    return true;
}

void solve() {
    cin >> n;

    for (int i = 1; i <= n; ++i) {
        for (int j = 1; j <= n; ++j) {
            cin >> g[i][j];
            revG[j][i] = g[i][j];
        }
    }

    int l = -1;
    int r = 1e9;

    while (r - l > 1) {
        int m = (l + r) / 2;

        //cout << m << " " << can(m) << endl;

        if (can(m)) {
            r = m;
        } else {
            l = m;
        }
    }

    if (can(r)) {
        cout << r;
    } else {
        cout << -1;
    }
}

int main() {
    auto start = chrono::steady_clock::now();
    ios_base::sync_with_stdio(0);
    cin.tie(nullptr); cout.tie(nullptr);
    /// =========================================
    /// fin("input.txt"); fout("output.txt");
    fin("avia.in"); fout("avia.out");
    /// cin >> TN;
    /// =========================================
    while (TN--) solve();
    auto finish = chrono::steady_clock::now();
    auto elapsed_ms = chrono::duration_cast<chrono::milliseconds>(finish - start);
    cerr << endl << "Time: " << elapsed_ms.count() << " ms\n";
    return 0;
}