(Perfect Numbers) An integer is said to be a perfect number if the sum of its divisors, including 1 (but not the number itself), is equal to the number. For example, 6 is a perfect number, because 6 = 1 + 2 + 3. Write a function isPerfect that determines whether parameter number is a perfect number. Use this function in a program that determines and prints all the perfect numbers between 1 and 1000. Print the divisors of each perfect number to confirm that the number is indeed perfect. Challenge the power of your computer by testing numbers much larger than 1000.

The input consists of n (0<n<100) lines.
Each line consists of the upper limit value(range from 2 to 10000).
The last line of input consists of Int(-1).

The main function is provided, you only need to complete the function isPerfect and printSum :

#include <iostream>
using namespace std;

bool isPerfect( unsigned int ); // function prototype
void printSum( unsigned int ); // function prototype

int main()
{
   // cout << "Perfect integers between 1 and 1000:" << endl;
   int maxnum = 0;
   while(true){
      cin>>maxnum;
      if (maxnum == -1)
         break;
      // loop from 2 to maxnum
      for ( unsigned int j = 2; j <= maxnum; ++j )
      {
         // if current integer is perfect 
         if ( isPerfect( j ) ) 
            printSum( j ); // print it as sum of factors
      } // end for
      cout << endl;
   }

} // end main