using System;
using System.Collections.Generic;
using System.Linq;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            bool[] ret = new bool[n];
            for (int i = 0; i < n; i++) ret[i] = true;
            for (int i = 0; i < n; i++)
            {
                string[] s = Console.ReadLine().Split();
                for (int j = 0; j < n; j++)
                {
                    if (i == j) continue;
                    else if (!(s[j] == "nyanpass" || s[j] == "-")) ret[j] = false;
                }
            }
            int a = -1;
            for (int i = 0; i < n; i++)
            {
                if (ret[i])
                {
                    if (a == -1)
                    {
                        a = i + 1;
                    }
                    else
                    {
                        a = 999;
                    }
                }
            }
            Console.WriteLine(a <= 100 ? a : -1);
        }
    }
}