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

	return 0;
}

/**************************************************************
	Problem: 1060
	User: chenxuanyi
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/