We define the Perfect Number is apositiveinteger that is equal to the sum of all itspositivedivisors except itself.

Now, given an

integer

n, write a function that returns true when it is a perfect number and false when it is not.

Example:

Input:
 28

Output:
 True

Explanation:
 28 = 1 + 2 + 4 + 7 + 14

Note:The input numbernwill not exceed 100,000,000. (1e8)

class Solution {
    public boolean checkPerfectNumber(int num) {
        if (num <= 0) return false;

        int sum = 0;
        for (int i = 1; i * i <= num; i++){
            if (num % i == 0){
                sum += i;
                if (i * i != num){
                    sum += num / i;
                }
            }
        }

        return sum - num == num;
    }
}