#include <iostream>
#include <math.h>
#include <algorithm>
#include <functional>
#include <vector>
#include <typeinfo>
#include <climits>
#include <ctype.h>
#include <string>
#include <stdio.h>
using namespace std;
#define INIT cin.tie(0); ios::sync_with_stdio(false);
#define FOR(i, a, n) for (int i = a; i < n; i++)
#define REP(i, n) for(int i = 0; i < n; i++)

int main()
{
    INIT;

    int n;
    cin >> n;

    string S[n][n];
    REP(i, n){
        REP(j, n){
            cin >> S[i][j];
        }
    }

    int c1, c2 = 0, idx = -1;
    REP(i, n){
        c1 = 0;
        REP(j, n){
            if(i != j){
                if(S[j][i] == "nyanpass") c1++;
            }
        }
        if(c1 == n - 1){
            c2++;
            idx = i + 1;
        }
        if(c2 > 1){
            idx = -1;
            break;
        }
    }
    cout << idx << endl;

    return 0;
}