#include <iostream>
#include <vector>
#include <string>
#include <numeric>
using namespace std;

int main()
{
	int N;
	string str;

	cin >> N;
	vector<vector<int> > A(N + 1, vector<int>(N + 1, 0));

	for (int i = 1; i <= N; i++) {
		for (int j = 1; j <= N; j++) {
			cin >> str;
			A[j][i] = (str == "nyanpass" ? 1 : 0);
		}
	}
	int nyancount = 0, nyan;
	for (int i = 1; i <= N; i++) {
		if (accumulate(A[i].begin(), A[i].end(), 0) == N - 1) {
			nyancount++;
			nyan = i;
		}
	}

	if (nyancount == 1)
		cout << nyan << endl;
	else
		cout << -1 << endl;

	return 0;
}