using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace foryuki
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            bool[] b = new bool[n];

            for (int i = 0; i < b.Length; i++)
            {
                b[i] = true;
            }

            for (int i = 0; i < n; i++)
            {
                string[] s = Console.ReadLine().Split();
                for (int j = 0; j < s.Length; j++)
                {
                    if (s[j] != "nyanpass")
                    {
                        if (s[j] != "-")
                        {
                            b[j] = false;
                        }
                    }
                }
            }

            if (b.Where(x => x == true).Count() != 1)
            {
                Console.WriteLine(-1);
            }
            else
            {
                for (int i = 0; i < n; i++)
                {
                    if (b[i])
                    {
                        Console.WriteLine(i + 1);
                        break;
                    }
                }
            }
        }

        //-------------------------------------------------------------

        static int[] ConvertStringArrayToIntArray(string[] array)
        {
            return Array.ConvertAll(array, str => int.Parse(str));
        }

        static List<int> ConvertStringArrayToIntList(string[] str)
        {
            var list = new List<int>();
            foreach (var c in str) list.Add(int.Parse(c));
            return list;
        }
    }
}