#include <bits/stdc++.h>
using namespace std;
int main(){
    int a,i,s=0;
    cin>>a;
    if(a%2==0){
    for(i=1;i<=a;i++){
        if(a%i==0){
            s=s+i;
        }
    }cout<<s<<endl;
}   else{
    for(i=2;i<a;i=i+2){
        s=s+i;
    }cout<<s;
}
}
/**************************************************************
	Problem: 1060
	User: wangchenyu
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/