#include<bits/stdc++.h>
using namespace std;
int main(){
    int i,a,b=0,n,h=0;
    cin>>n;
    if(n%2==1){
        for(i=1;i<=n;i+=1){
            if(i%2==0){
                h=h+i;  
            }
        }
        cout<<h;      
    }
    else{
        for(a=1;a<=n;a++){
            if(n%a==0){
                b=b+a;
            }
        }
        cout<<b;  
    }
} 
 
/**************************************************************
	Problem: 1060
	User: hongjiaming
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/