#include "bits/stdc++.h"

using namespace std;
using ll = long long;
const double pi = acos(-1);
#define FOR(i,a,b) for (ll i=(a),__last_##i=(b);i<__last_##i;i++)
#define RFOR(i,a,b) for (ll i=(b)-1,__last_##i=(a);i>=__last_##i;i--)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) RFOR(i,0,n)
#define __GET_MACRO3(_1, _2, _3, NAME, ...) NAME
#define rep(...) __GET_MACRO3(__VA_ARGS__, FOR, REP)(__VA_ARGS__)
#define rrep(...) __GET_MACRO3(__VA_ARGS__, RFOR, RREP)(__VA_ARGS__)
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v) {
	REP(i, v.size()) { if (i)os << " "; os << v[i]; }return os;
}
template<typename T> ostream& operator<<(ostream& os, const vector<vector<T>>& v) {
	REP(i, v.size()) { if (i)os << endl; os << v[i]; }return os;
}

const ll INF = 1LL << 60;
ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	ll n;

	cin >> n;

	vector<vector<string>> v(n, vector<string>(n));
	vector<ll> vv;
	bool flag;

	REP(i, n) {
		REP(j, n) {
			cin >> v[i][j];
		}
	}

	REP(i, n) {
		flag = true;
		REP(j, n) {
			if (i != j && v[j][i] != "nyanpass") {
				flag = false;
				break;
			}
		}
		if (flag) {
			vv.push_back(i + 1);
		}
	}

	if (vv.size() == 1) {
		cout << vv[0] << endl;
	}
	else {
		cout << -1 << endl;
	}
}