#include<bits/stdc++.h>
using namespace std;
int n,t,qi,he;
int main()
{
	cin>>n;
	t=n;
	for (int i=1;i<=n;i++)
	{
		if (i%2==0) qi+=i;
		if (n%i==0) he+=i;
	}
	if (t%2==0) cout<<he;
		else cout<<qi;
}