#include<iostream>
#include<fstream>
#include<sstream>
#include<string>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<vector>
#include<list>
#include<algorithm>
#include<utility>
#include<complex>
#include<functional>
using namespace std;



int main(void){
	int N;
	cin >> N;
	vector<bool> flag(N,true);
	for (int i = 0; i < N; i++)
		for (int j = 0; j < N; j++){
			string s;
			cin >> s;
			if (i != j)flag[j]= flag[j]&(s == "nyanpass");
		}
	int cnt = 0, res = -1;
	for (int i = 0; i < N; i++)
		if (flag[i])cnt++, res = i + 1;
	if (cnt == 1)cout << res << endl;
	else cout << -1 << endl;
	return(0);
}