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

namespace Tier_II
{
    class Program
    {
        public static int[][] ReadDoubleMatrix(string path)
        {
            StreamReader f = new StreamReader(path);
            int m = int.Parse(f.ReadLine());
            int[][] matrix = new int[m][];
            for (int i = 0; i < matrix.Length; i++)
            {
                string[] strs = f.ReadLine().Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
                int[] ai = new int[strs.Length];
                for (int j = 0; j < ai.Length; j++)
                {
                    ai[j] = int.Parse(strs[j]);
                }
                matrix[i] = ai;
            }
            f.Close();
            return matrix;
        }

        static void Main(string[] args)
        {
            string path = Console.ReadLine();
            int max = -1;
            int[][] matrix = ReadDoubleMatrix(path);
            for (int i = 0; i<matrix.Length;i++)
            {
                int[] matrix1 = matrix[i];
                for(int j=0; j<matrix1.Length;j++)
                {
                    if (matrix1[j] == 0)
                    {
                        max = i;
                        continue;
                    }
                }
            }
            Console.WriteLine(max);
            Console.ReadLine();
        }
    }
}