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

class Program
{
    public void Proc()
    {
        Reader.IsDebug = false;
        int murabitoCount = int.Parse(Reader.ReadLine());
        this.aisatu = new string[murabitoCount,murabitoCount];
        for(int i=0; i<murabitoCount; i++) {
            string[] inpt = Reader.ReadLine().Split(' ');
            for(int j=0; j<inpt.Length; j++) {
                this.aisatu[i,j] = inpt[j];
            }
        }
        List<int> nyan = new List<int>();
        for(int i=0; i<this.aisatu.GetLength(1); i++) {
            bool isNyan = true;
            for(int j=0; j<this.aisatu.GetLength(0); j++) {
                if(i != j && (!this.aisatu[j,i].Equals("nyanpass"))) {
                    isNyan = false;
                    break;
                }
            }
            if(isNyan) {
                nyan.Add(i+1);
            }
        }
        if(nyan.Count == 1) {
            Console.WriteLine(nyan[0]);
        } else
        {
            Console.WriteLine(-1);
        }
    }
    
    string[,] aisatu;

    public class Reader
    {
        public static bool IsDebug = true;
        private static String PlainInput = @"


2
- ohayo
zukoo -


 
";
        private static System.IO.StringReader Sr = null;
        public static string ReadLine()
        {
            if (IsDebug)
            {
                if (Sr == null)
                {
                    Sr = new System.IO.StringReader(PlainInput.Trim());
                }
                return Sr.ReadLine();
            }
            else
            {
                return Console.ReadLine();
            }
        }
        public static int[] GetInt(char delimiter = ' ', bool trim = false)
        {
            string inptStr = ReadLine();
            if (trim)
            {
                inptStr = inptStr.Trim();
            }
            string[] inpt = inptStr.Split(delimiter);
            int[] ret = new int[inpt.Length];
            for (int i = 0; i < inpt.Length; i++)
            {
                ret[i] = int.Parse(inpt[i]);
            }
            return ret;
        }
    }
    static void Main()
    {
        Program prg = new Program();
        prg.Proc();
    }
}