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

/**************************************************************
	Problem: 1060
	User: houshanglin
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/