#include <bits/stdc++.h>
#define int long long
using namespace std;
using Graph = vector<vector<int>>;

signed main(){
  int N;
  cin >> N;
  
  vector<vector<string>> A(N, vector<string>(N));
  for( int i = 0; i < N; i++ ){
    for( int j = 0; j < N; j++ ){
      cin >> A.at(i).at(j);
    }
  }
  
  int ans = -1;
  for( int i = 0; i < N; i++ ){
    bool fg = true;
    for( int j = 0; j < N; j++ ){
      if( A.at(j).at(i) != "nyanpass" && j != i ) fg = false;
    }
    if( ans == -1 && fg ) ans = i+1;
    else if( ans != -1 && fg ){
      cout << -1 << endl;
      return 0;
    }
  }
  
  cout << ans << endl;
  
  
  
}