#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    int s = 0;
    cin >> n;
    if ( n % 2 != 0)
    {
        for (int i = 2; i <=n;i+=2)
        {
            s += i;
        }
    }
    else
    {
        for (int i = 1;i<=sqrt(n);i++)
        {
            if(n % i ==0) 
            {
                if ( i != n/i)
                {
                    s += i;
                    s += n / i;
                }
                else
                {
                    s += i;
                }
 
            }
        }
    }
 
    cout << s;
 
    return 0;
}
/**************************************************************
	Problem: 1060
	User: linmiaoling
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/