#include <iostream>
#include<vector>

using namespace std;

int main() {
  int n;
  cin >> n;
  vector< vector<string> > greet_table;
  for (int i = 0; i < n; i++) {
    vector<string> greet_row;
    for (int j = 0; j < n; j++) {
      string str;
      cin >> str;
      greet_row.push_back(str);
    }
    greet_table.push_back(greet_row);
  }

  int renge = -1;

  for (int i = 0; i < n; i++) {
    bool flag = false;
    for (int j = 0; j < n; j++) {
      if (i == j) {
        continue;
      }
      if (greet_table[j][i] != "nyanpass") {
        flag = true;
        break;
      }
    }
    if (flag) {
      continue;
    }
    if (renge == -1) {
      renge = i + 1;
    } else {
      renge = -1;
      break;
    }
  }

  cout << renge << endl;
  return 0;
}