public class equalSum{
    public int equalSum()
    {
        return equalSum(a,0,0,0);
    }

    public int equalSum(int[] a, int i, int sum1, int sum2)
    {
        if(sum1 == sum2)
        {
            return i;
        }
        if(i == a.length-1)
        {
            return -1;
        }
        return equalSum(a,i+1, sum1(a,0,i,0), sum2(a,i,0));

    }
    public int sum1(int[]a, int j, int num, int sum1) //num = i
    {
        if(j == num)
        {
            return sum1;
        }
        return sum1(a,j+1,num, sum1+a[j]);

    }
      public int sum2(int[]a, int j, int sum2) //num = i
    {

        if(j == a.length-1)
        {
            return sum2;
        }
        return sum2(a,j+1,sum2+a[j]);

    }

}