using System;

public class Program

{

    public static void Main()

    {

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

        Console.WriteLine(Solution(arr));

    }

    public static int Solution (int[] A)

    {

        int count = 0;

        int multiply = 0;

        foreach (int car in A)

        {

            if (car == 0)

            {

                multiply = multiply + 1;

            }

            if (multiply > 0)

            {

                if (car == 1)

                {

                    count = count + multiply;

                    if (count > 1000000000)

                    {

                        return -1;

                    }

                }

            }

        }

        return count;

    }

}