#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#include<vector>
#include<map>
#include<queue>
#include<string>
#include<sstream>
#include<cmath>
using namespace std;

int 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[i][j];
    }
  }

  vector<int> ren(n);
  for(int i=0; i<n; i++){
    for(int j=0; j<n; j++){
      if( i == j ) continue;
      if( a[i][j] != "nyanpass" ){
        ren[j] = -1;
      }
    }
  }

  int cnt = 0;
  int p = 0;
  for(int i=0; i<n; i++){
    if( ren[i] != -1 ) cnt++;
    if( ren[i] == 0 ) p = i+1;
  }
  if( cnt != 1 ) cout << -1 << endl;
  else cout << p << endl;

  return 0;
}