#include <vector>
#include <string>
#include <algorithm>
#include <numeric>
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <utility>
#include <list>
#include <functional>
#include <queue>
#include <map>
#include <iterator>
#include <iomanip>
#include <complex>
using namespace std;

using ull = unsigned long long;
using ll = long long;


int main()
{
  int n;
  cin >> n;
  vector<vector<string>> board(n,vector<string>(n));

  for(auto&& y : board)
    for(auto&& x : y)
      cin >> x;

  int result = -1;

  for(int i = 0; i < n; ++i)
  {
    bool check = true;
    for(int j = 0; j < n; ++j)
    {
      check &= (board.at(j).at(i) == "nyanpass" || board.at(j).at(i) == "-");
    }

    if(check && result == -1)
      result = i+1;
    else if(check)
    {
      cout << -1 << endl;
      return 0;
    }
    
  }

  cout << result << endl;
}