import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static long sumOfGroup(long k) {
        long s = k*(k+1);
        s=s-1;
        long sum = 0;
        for(long i=k; k > 0; k--){
            sum =sum+s;
            s-=2;
        }
        return sum;
        
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long k = in.nextLong();
        long answer = sumOfGroup(k);
        System.out.println(answer);
        in.close();
    }
}