#include <iostream>
using namespace std;

bool isAFactor(int a, int b)
{
  return ((a % b) == 0);
}

int main()
{
  int startval, endval;

  cout << "This program will find all perfect numbers given a range of number.\n";

  cout << "Please select a start value: " ;
  cin >> startval;

  cout << "Please select an end value: " ;
  cin >> endval;

  if (endval < startval)
  {
    cout << "Error: The end value must be greater than the start value.\n";
    return 0;
  }

  int runningTotal = 0;
  bool found = false;

  for (int i = startval; i <= endval; i++)
  {
    for(int j = 1; j <= i / 2; j++)
    {
      if (isAFactor(i, j))
      {
        runningTotal += j;
      }
    }

    if (runningTotal == i)
    {
      cout << "Perfect Number found : " << runningTotal << "\n";
      found = true;
    }

    runningTotal = 0;
  }

  if (found == false)
  {
    cout << "There is no perfect number between " << startval << " and " << endval << ".\n";
  }

  return 0;
}