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 number n will not exceed 100,000,000. (1e8)

class Solution {
public:
    bool checkPerfectNumber(int num) {
        if(num<1 ) return false;
        int s=sqrt(num);
        bool flag= s*s==num;
        int sum =1 +flag*s;
        for(int i=2;i<s+!flag;i++)
            if(num%i==0) sum+=i+num/i ;
​
        return sum == num;
​
​
    }
};