public int divisorSum(int n) {
        
   if (n == 1) return 1;
        
   int sum = 0;
          
   for (int div = 1; div*div <= n; div++){
      sum +=  n % div == 0 ? div + n / div : 0;
   }
                       
   return Math.sqrt(n) % 1 == 0 ? sum - (int) Math.sqrt(n) : sum;
}