#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <fstream>
#include <sstream>
#include<set>
#include<stack>
#include<time.h>
#include <sys/types.h>
#include <tuple>
#include <numeric>
#include <iterator>

typedef long long int ll;
//#include<bits/stdc++.h>


using namespace std;





int main()
{

    int Q;
    Q = 1;
    //cin >> Q;


    while (Q--) {
        int n;
        cin >> n;
        vector<bool>f(n + 1);
        for (int i = 0; i < n; i++)f[i] = 1;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                
                string p;
                cin >> p;
                if (i == j)continue;
                if (p == "nyanpass")continue;
                f[j] = 0;
            }
        }
        int t = -1;
        int p = 0;
        for (int i = 0; i < n; i++) {
            
            if (!f[i])continue;
            t = i + 1;
            p++;
        }
        if (p > 1)t = -1;
        cout << t;
    }
    return 0;
}