#include <bits/stdc++.h>
#include "bits/stdc++.h"
#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <string>
#include <sstream>
#include <cmath>
#include <stack>
#include <queue>
#include <cctype>
#include <stdio.h>
#include <map>
#include <unordered_map>
#include <string.h>
#include <utility>

typedef long long ll;
const int INF = 1e8;

#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
using namespace std;

typedef pair<int, int> P;

bool judge[101];

int main() {

	int n = 0;
	cin >> n;

	for(int i=0; i<100; i++){
		judge[i] = true;
	}

	string s;
	for(int i=0; i<n; i++){
		for(int j=0; j<n; j++){
			cin>>s;
			if(i !=j){

				if(s !="nyanpass"){
					judge[j] =false;
				}

			}
		}
	}
	vector<int> ans;
	for(int i=0; i<n; i++){
		if(judge[i]){
			ans.push_back(i+1);
		}
	}
	if(ans.size() ==1){
		cout<<ans[0]<<endl;
	}else {
		cout<<-1<<endl;
	}

	return 0;
}