#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int n;
  cin >> n;
  vector a(n, vector<string>(n));
  rep(i, n) rep(j, n) cin >> a[i][j];
  vector<int> cand(0);
  rep(j, n) {
    bool ok = true;
    rep(i, n) {
      if (i == j) continue;
      if (a[i][j] != "nyanpass") ok = false;
    }
    if (ok) cand.push_back(j);
  }
  if (cand.size() == 1)
    cout << cand[0] + 1 << endl;
  else
    cout << -1 << endl;
  return 0;
}