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

public class Solution {

    static long sumOfGroup2(long k) {
        long n = k*k + 1 - k;
        return k*n + (k-1)*k;

    }
    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        return sumOfGroup2(k);
    }

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