#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (n); i++)
#define rep1(i, n) for(int i = 1; i <= (n); i++)
#define co(x) cout << (x) << "\n"
#define cosp(x) cout << (x) << " "
#define ce(x) cerr << (x) << "\n"
#define cesp(x) cerr << (x) << " "
#define pb push_back
#define mp make_pair
#define Would
#define you
#define please

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);


	int N;
	cin >> N;
	int notR[101] = {};
	rep(i, N) rep(j, N) {
		string S;
		cin >> S;
		if (i == j) continue;
		if (S != "nyanpass") notR[j] = 1;
	}

	int iru = 0;
	int hutari = 0;
	rep(i, N) {
		if (!notR[i]) {
			if (iru) hutari = 1;
			iru = i + 1;
		}
	}

	if (hutari) co(-1);
	else {
		if (iru) co(iru);
		else co(-1);
	}


	Would you please return 0;
}