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

}

/**************************************************************
	Problem: 1060
	User: 15159808820
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/