#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
    int n;
    cin >> n;
    bool v[n];
    fill(v, v+n, true);
    for (int i = 0; i < n; i++)
        for (int j = 0; j < n; j++) {
            string s;
            cin >> s;
            if (i == j) continue;
            if (s != "nyanpass") v[j] = false;
        }
    int cnt = 0;
    int ans;
    for (int i = 0; i < n; i++)
        if (v[i]) {
            cnt++;
            ans = i+1;
        }
    cout << (cnt == 1 ? ans : -1 ) << endl;
    return 0;
}