#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: wengzihang
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/