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

namespace YukiCoderNo239
{
    class Program
    {
        static void Main()
        {
            int length = LIB.IO.R<int>();
            int output = -1;
            string[][] greeding = LIB.IO.R<string>(length, ' ');
            int okcount = 0;

            for (int i = 0; i < length; i++)
            {
                bool flag = true;
                for (int j = 0; j < length; j++)
                {
                    if (!((greeding[i][j] == "nyanpass") || (i == j)))
                    {
                        flag = false;
                        break;
                    }
                }
                if (flag == true)
                {
                    output = i + 1;
                    if (okcount >= 1)
                    {
                        LIB.IO.W(-1);
                        LIB.IO.WFLUSH();
                        return;
                    }
                    okcount++;
                }
            }
            for (int i = 0; i < length; i++)
            {
                bool flag = true;
                for (int j = 0; j < length; j++)
                {
                    if (!((greeding[j][i] == "nyanpass") || (i == j)))
                    {
                        flag = false;
                        break;
                    }
                }
                if (flag == true)
                {
                    if (okcount >= 1)
                    {
                        if (output != i + 1)
                        {
                            LIB.IO.W(-1);
                            LIB.IO.WFLUSH();
                            return;
                        }
                    }
                    output = i + 1;
                    okcount++;
                }
            }
            LIB.IO.W(output);
            LIB.IO.WFLUSH();
        }
    }
}
namespace LIB
{
    public class IO
    {
        private const int WMAX = 1000;
        private static string WSTRING = "";
        public static T R<T>()
        {
            return (T)(Convert.ChangeType(R(), typeof(T)));
        }
        public static T[] R<T>(char splitter = ' ')
        {
            return R().Split(splitter).Select(v => UTILITY.PARSE<T>(v)).ToArray();
        }
        public static T[] R<T>(int length)
        {

            T[] ret = new T[length];
            for (int i = 0; i < length; i++)
            {
                ret[i] = R<T>();
            }
            return ret;
        }
        public static T[][] R<T>(int length, char splitter = ' ')
        {
            T[][] ret = new T[length][];
            for (int i = 0; i < length; i++)
            {
                ret[i] = R<T>(splitter);
            }
            return ret;
        }
        private static string R()
        {
            return Console.ReadLine();
        }
        public static void W(object value, bool addLineFeed = true)
        {
            WSTRING += UTILITY.PARSE<string>(value);
            if (addLineFeed == true) { WSTRING += "\n"; }
            if (WSTRING.Count() >= WMAX) { WFLUSH(); }
        }
        public static void WFLUSH()
        {
            Console.Write(WSTRING);
            WSTRING = "";
        }
    }
    public class UTILITY
    {
        public static T PARSE<T>(object value)
        {
            return (T)(Convert.ChangeType(value, typeof(T)));
        }
    }
}