#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<int(n); i++)
#define FOR(i,m,n) for(int i=int(m); i<int(n); i++)
#define ALL(obj) (obj).begin(),(obj).end()
#define VI vector<int>
#define VLL vector<long long>
#define VVI vector<vector<int>>
#define VVLL vector<vector<long long>>
#define VC vector<char>
#define VS vector<string>
#define VVC vector<vector<char>>
#define fore(i,a) for(auto &i:a)
typedef long long ll;
typedef pair <int, int> P;
template<class T> bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
const int  INF = 2147483647;
const ll INFL = 9223372036854775807;
const ll mod = 1000000007;



int main() {
	int n;
	cin >> n;
	VI v(n, 0);
	REP(i, n) {
		REP(j, n) {
			string s;
			cin >> s;
			if (s == "nyanpass") {
				v[i]++;
				v[j]++;
			}
		}
	}
	int ans = -1;
	REP(i, n) {
		if (v[i] == n - 1) {
			if (ans == -1)ans = i;
			else {
				cout << -1 << endl;
				return 0;
			}
		}
	}
	REP(i, n) {
		if (i == ans)continue;
		if (v[i] != 1) {
			cout << -1 << endl;
			return 0;
		}
	}
	cout << ans + 1 << endl;


	return 0;
}