#include <algorithm>
#include <iostream>
#include <iomanip>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <cmath>
using namespace std;

#define FOR(i,s,e) for (int i = int(s); i != int(e); i++)
#define FORIT(i,c) for (typeof((c).begin()) i = (c).begin(); i != (c).end(); i++)
#define ISEQ(c) (c).begin(), (c).end()

int main(){
	int N;
	cin >> N;
	string s[N][N];
	FOR(i,0,N){
		FOR(j,0,N){
			cin >> s[i][j];
		}
	}

	bool isNyanpass[N];

	FOR(j,0,N){
		isNyanpass[j] = true;
		FOR(i,0,N){
			if(i != j && s[i][j] != "nyanpass"){
				isNyanpass[j] = false;
			}
		}
	}

	int ans = -1;
	FOR(i,0,N){
		if (isNyanpass[i]){
			if(ans == -1) ans = i+1;
			else{
				ans = -1;
				break;
			}
		}
	}

	cout << ans << endl;
	return 0;
}