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

namespace Solver
{
    interface Output
    {
        void Write(object str);
        void WriteLine(object str);
    }

    interface Input
    {
        int NextInt();
        string NextString();
    }

    class Console_ : Input, Output
    {
        Queue<string> param = new Queue<string>();
        int Input.NextInt()
        {
            if (param.Count == 0)
            {
                foreach (var item in Console.ReadLine().Split(' '))
                {
                    param.Enqueue(item);
                }
            }
            return int.Parse(param.Dequeue());
        }
        string Input.NextString()
        {
            if (param.Count == 0)
            {
                foreach (var item in Console.ReadLine().Split(' '))
                {
                    param.Enqueue(item);
                }
            }
            return param.Dequeue();
        }
        void Output.Write(object obj)
        {
            System.Console.Write(obj);
        }
        void Output.WriteLine(object obj)
        {
            System.Console.WriteLine(obj);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            new Solver(new Console_(), new Console_()).Run();
        }
    }

    class Debug_ : Input
    {
        int i = 0;
        int Input.NextInt()
        {
            return (int)data[i++];
        }
        string Input.NextString()
        {
            return (string)data[i++];
        }
        object[] data =
        {
            1,
            2,
            2,
            2
        };
    }

    class Solver
    {
        Input input;
        Output output;
        public Solver(Input input, Output output)
        {
            this.input = input;
            this.output = output;
        }

        public void Run()
        {
            int N = input.NextInt();
            var greeting = Enumerable.Repeat(true, N).ToArray();
            for (int i = 0; i < N; ++i)
            {
                for (int j = 0; j < N; ++j)
                {
                    var str = input.NextString();
                    greeting[j] &= (str == "nyanpass" || str == "-");
                }
            }
            int ren = -1;
            for (int i = 0; i < N; ++i)
            {
                if (greeting[i])
                {
                    if (ren == -1)
                    {
                        ren = i + 1;
                    }
                    else
                    {
                        output.WriteLine(-1);
                        return;
                    }
                }
            }
            output.WriteLine(ren);
        }
    }
}