module main;

import std;

void main()
{
	// 入力
	auto N = readln.chomp.to!int;
	auto A = new string[][](N);
	foreach (ref a; A)
		a = readln.split;
	// 答えの計算
	int[] ans;
	foreach (x; 0 .. N) {
		bool ok = true;
		foreach (y; 0 .. N) {
			if (y == x)
				continue;
			if (A[y][x] != "nyanpass") {
				ok = false;
				break;
			}
		}
		if (ok)
			ans ~= x + 1;
	}
	// 答えの出力
	writeln(ans.length == 1 ? ans[0] : -1);
}