using System;

public class Program

{

    static int zero (int []arr)

    {

        int left=0;

        int right=arr.Length -1;

        while (left <right)

        {

            int mid =(left+right)/2;

            if (arr [mid]==0)

            {

                if (arr [mid+1]==1)

                    return mid;

                left=mid+1;

            }

            else

            {

                if (arr [mid-1]==0)

                    return mid;

                right=mid+1;

            }

        }

        return -1;

    }

    public static void Main()

    {

        int []arr ={0,0,0,0,1,1,1};

        Console.WriteLine(zero (arr));

    }

}