#include<bits/stdc++.h>
using namespace std;
int main() {
int n;
cin >> n;
int sum = 0;
if (n % 2 == 1) {
int m = n / 2;
sum = m * (m + 1);
}
else {
    for (int i = 1; i <= n; ++i) {
    if (n % i == 0) sum += i;
        }
    }
    cout << sum;
    return 0;
} 
/**************************************************************
	Problem: 1060
	User: zkl
	Language: C
	Result: Compile Error
****************************************************************/