#include <bits/stdc++.h>
#define rep(i, a) for (int i = 0; i < (a); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 7;

int N;
string A[100][100];

int main() {
    cin >> N;
    rep (i, N) rep (j, N) cin >> A[i][j];

    vector<int> cand;

    rep (j, N) {
        bool all = true;
        rep (i, N) if (i != j) {
            all &= A[i][j] == "nyanpass";
        }
        if (all) cand.push_back(j);
    }

    if (cand.size() == 1) {
        cout << cand[0] + 1 << endl;
    } else {
        cout << -1 << endl;
    }
    return 0;
}