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

namespace No236
{
	class MainClass
	{
		public static void Main (string[] args)
		{
			var n = Convert.ToInt32(Console.ReadLine ());

			List<bool>[] matrix = new List<bool>[n];
			for (int i = 0; i < n; i++) {
				matrix [i] = Console.ReadLine ().Split (' ').Select (v => {
					if(v == "-" || v == "nyanpass")
					{
						return true;
					}
					return false;
				}).ToList ();
			}
			List<bool> result = new List<bool> ();
			for (int x = 0; x < n; x++) {
				bool ok = true;
				for (int y = 0; y < n; y++) {
					if (!matrix [y] [x]) {
						ok = false;
						break;
					}
				}
				result.Add (ok);
			}
			if (result.Count (v => v) == 1) {
				var index = result.IndexOf (true) + 1;
				Console.WriteLine (index.ToString ());
				return;
			}
			Console.WriteLine ("-1");
		}
	}
}