#include <iostream>
#include <iomanip>
#include <cmath>

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: admin
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/