#include <cstdio>  // {{{
#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>

#define GET_MACRO(a, b, c, d, NAME, ...) NAME
#define REP(...) GET_MACRO(__VA_ARGS__, REP4, REP3, REP2)(__VA_ARGS__)
#define REP2(i, a) REP3(i, 0, a)
#define REP3(i, a, b) REP4(i, a, b, 1)
#define REP4(i, a, b, s) for (int i = (a); i < (int)(b); i += (s))
#define REPR(...) GET_MACRO(__VA_ARGS__, REPR4, REPR3, REPR2)(__VA_ARGS__)
#define REPR2(i, a) REPR3(i, 0, a)
#define REPR3(i, a, b) REPR4(i, a, b, 1)
#define REPR4(i, a, b, s) for (int i = (b)-1; i >= (int)(a); i -= (s))
#define ALL(c) (c).begin(), (c).end()

using Int = long long;
// clang-format off
template<typename T,typename U>inline bool chmax(T&x,U a){return x<a&&(x=a,1);}
template<typename T,typename U>inline bool chmin(T&x,U a){return a<x&&(x=a,1);}
inline signed in(){signed x;scanf("%d",&x);return x;}
// clang-format on
// }}}

using namespace std;

template <typename T>
using Mat = vector<vector<T>>;
template <typename T>
Mat<T> buildMat(int R, int C) {
  return move(Mat<T>(R, vector<T>(C)));
}
signed main() {
  int N = in();
  auto A = buildMat<string>(N, N);
  REP(i, N) REP(j, N) cin >> A[i][j];

  vector<int> cand;
  REP(i, N) {
    bool ok = true;
    REP(j, N) {
      if (i == j) continue;
      ok = ok && A[j][i] == "nyanpass";
    }
    if (ok) cand.emplace_back(i + 1);
  }
  if (cand.size() == 1) {
    cout << cand[0] << endl;
  } else {
    puts("-1");
  }

  return 0;
}