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

signed main(){
  int N; cin >> N;
  vector< vector< string > > mat( N, vector< string >( N ) );
  for( int i = 0; i < N; ++i )
    for( int j = 0; j < N; ++j )
      cin >> mat[ i ][ j ];
  int ans = -1;
  for( int j = 0; j < N; ++j ){
    int ng = 0;
    for( int i = 0; i < N; ++i ) if( i != j )
      ng |= mat[ i ][ j ] != "nyanpass";
    if( not ng ){
      if( ans != -1 )
        cout << -1 << endl,
        exit( 0 );
      else
        ans = j + 1;
    }
  }
  cout << ans << endl;
  return 0;
}