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

int main() {
  int N;
  string S;
  cin >> N;
  vector<int> V(N);
  for (int i = 0; i < N; i++)
    for (int j = 0; j < N && cin >> S; j++)
      if (S != "nyanpass" && S != "-") V.at(j)++;
  int ans = 0, cnt = 0;
  for (int i = 0; i < N; i++) if (!(V.at(i))) cnt++, ans = i + 1;
  cout << ((cnt == 1) ? ans : -1) << "\n";
}