using System;

public class Program {
    public static void Main() {
        int n = int.Parse(Console.ReadLine());
        bool[] renchon = new bool[n];
        for (int i = 0; i < n; i++) renchon[i] = true;
        for (int i = 0; i < n; i++) {
            string[] greeting = Console.ReadLine().Split();
            for (int j = 0; j < n; j++) {
                if (greeting[j] != "nyanpass") {
                    renchon[j] = false;
                }
            }
        }
        int index = -1;
        for (int i = 0; i < n; i++) {
            if (renchon[i]) {
                if (index == -1) {
                    index = i;
                } else {
                    Console.WriteLine(-1);
                    return;
                }
            }
        }
        if (index == -1) Console.WriteLine(-1);
        else Console.WriteLine(index+1);
    }
}