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

public class Solution {

    static long sumOfGroup(int k) {
        BigInteger result=BigInteger.ZERO;
        
        BigInteger K = BigInteger.valueOf(k);
        BigInteger K_minus_1 = BigInteger.valueOf(k-1);
        
        BigInteger first = K.multiply(K_minus_1).add(BigInteger.ONE);
        //System.err.println("first=" + first);
        result = K.multiply(first);
        result = result.add(K.multiply(K_minus_1));
        return result.longValue();
    }

    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();
    }
}