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

int main() {
	int n;
	cin >> n;

	vector<bool> renchon_ppoi(n, true);
	for (int i = 0; i < n; i++)
	{
		for (int k = 0; k < n; k++)
		{
			string str;
			cin >> str;
			if ((i != k) && (str != "nyanpass"))
			{
				renchon_ppoi[k] = false;
			}
		}
	}

	int renchon = -1, count = 0;
	for (int i = 0; i < n; i++)
	{
		if (renchon_ppoi[i])
		{
			count++;
			renchon = i + 1;
			if (count > 1)
			{
				renchon = -1;
				break;
			}
		}
	}
	cout << renchon << endl;

	return 0;
}