#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 1e4 + 10, INF = 0x3f3f3f3f, MOD = 1E9 + 7;
int n, m, x, p[N];
struct Node {
    int u, v, w;
    bool operator<(const Node& r) const { return w < r.w; }
} g[N << 1];

int find(int u) {
    return u == p[u] ? u : p[u] = find(p[u]);
}
void kruskal() {
    for (int i = 0; i <= n; i++)
        p[i] = i;
    sort(g + 1, g + 1 + m);
    int ans = 0, cnt = 0;
    for (int i = 1; i <= m; i++) {
        int u = g[i].u, v = g[i].v, w = g[i].w;
        int fu = find(u), fv = find(v);
        if (fu != fv)
            p[fu] = fv, ans += w, cnt++;
    }
    if (cnt != n - 1)
        ans = -1;
    cout << ans << endl;
}
int main(int argc, char* argv[]) {
    cin >> n;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++) {
            cin >> x;
            g[++m] = {i, j, x};
            g[++m] = {j, i, x};
        }
    kruskal();
    return 0;
}