#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
using namespace std;
typedef long long LL;
typedef vector<int> VI;

int main() {
	int n;
	cin >> n;
	string a[100][100];
	vector<bool> b(n, true);
	REP(i, n) {
		REP(j, n) {
			cin >> a[i][j];
			if (a[i][j] != "nyanpass" && i != j) b[j] = false;
		}
	}
	int ans = -1;
	REP(i, n) {
		if (b[i]) {
			if (ans == -1) {
				ans = i + 1;
			}
			else {
				ans = -1;
				break;
			}
		}
	}
	cout << ans << endl;
	return 0;
}