#include <iostream>
#include <string>
using namespace std;

int main() {
  int n;
  cin >> n;
  string a[100][100];
  for (int i = 0; i < n; ++i) for (int j = 0; j < n; ++j) cin >> a[i][j];
  int res = -1;
  for (int i = 0; i < n; ++i) {
    bool flg = true;
    for (int j = 0; j < n && flg; ++j) {
      if (a[j][i] != "nyanpass" && i != j) {
        flg = false;
      }
    }
    if (flg) {
      if (res == -1) {
        res = i + 1;
      } else {
        cout << -1 << endl;
        return 0;
      }
    }
  }
  cout << res << endl;
  return 0;
}