//we could stop at sqrt(n)
//This is my Java solution. I think this may be better.

class Calculator implements AdvancedArithmetic{
    public int divisorSum(int n){
       int sum = 0;
       for(int i = 1; i <= (int)Math.sqrt(n); i++) {
           if(n%i==0){
               sum = sum + i + n/i;
           }
       }
       if((int)Math.sqrt(n)*(int)Math.sqrt(n)==n){
           sum -= Math.sqrt(n);
       }
        return sum;
    }
}