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

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