#include <bits/stdc++.h>

using namespace std;

#define REP(i, n) for(int i = 0; i < n; i++)

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n;
    cin >> n;
    string a[n][n];
    REP(i, n) {
        REP(j, n) cin >> a[i][j];
    }

    vector<int> candidate;
    REP(j, n) {
        int cnt = 0;
        REP(i, n) {
            if (a[i][j] == "nyanpass") cnt++;
        }
        if (cnt == n - 1) candidate.push_back(j + 1);
    }

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