import java.util.*;
public class Main {
  public int Moneycount(int k){
        int ans=0;
        int temp=0;
        int i;
        for ( i=0;i<k;i+=++temp){
            ans+=(temp*temp);

        }
        ans+=((k-i+temp)*temp);
        return ans;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int k = in.nextInt();
        Main k1=new Main();
        System.out.println(k1.Moneycount(k));

    }

}