#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,s=0;
	cin>>n;
	if(n%2!=0){
		for(int i=1;i<=n;i++){
			if(i%2==0) s=s+i;
		}
		
	}else{
		
		for(int i=1;i<=n;i++){
			if(n%i==0) s=s+i;
		}
	}
		
	cout<<s;
	
}
/**************************************************************
	Problem: 1060
	User: dengyuanyan
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/