#include <bits/stdc++.h>

using namespace std;

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

const double PI = acos(-1);

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

  int n; cin >> n;
  vector<bool> v(n, true);

  REP (i, n) {
    REP (j, n) {
      string s; cin >> s;
      if (j != i && s != "nyanpass")
        v[j] = false;
    }
  }

  if (count(v.begin(), v.end(), true) == 1)
    cout << find(v.begin(), v.end(), true) - v.begin() + 1 << endl;
  else
    cout << -1 << endl;
  
  return 0;
}