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


/**************************************************************
	Problem: 1060
	User: zhuangsongyu
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/