#include <iostream>
#include <iomanip>
typedef unsigned long long ul;
typedef signed long long ll;

int main(void)
{
  std::cin.tie(0);
  std::ios::sync_with_stdio(false);
  std::cout << std::fixed << std::setprecision(2);
  int n;
  std::cin >> n;
  bool canbe[n];
  std::fill(canbe, canbe+n, true);
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < n; ++j) {
      std::string s;
      std::cin >> s;
      if (i==j) continue;
      if (s != "nyanpass") canbe[j] = false;
    }
  }
  int ans = -1;
  for (int i = 0; i < n; ++i) {
    if (canbe[i]) {
      if (ans != -1) {std::cout << -1 << std::endl; return 0;}
      ans = i;
    }
  }
  std::cout << ans << std::endl;
  return 0;
}