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

/**************************************************************
	Problem: 1060
	User: zy002
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/