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


public class Solution {
  
  static BigInteger sumOfGroup(int k) {
    if (k==1)
      return BigInteger.ONE;
    BigInteger two = new BigInteger("2");
    BigInteger bk = new BigInteger(String.valueOf(k));
    BigInteger bk1 = new BigInteger(String.valueOf(k-1));
    BigInteger s = bk1.multiply(bk).divide(two);
    BigInteger result = BigInteger.ZERO;
    BigInteger cur;
    for(int i = 0 ; i <k ; i++) {
      cur = two.multiply(s.add(new BigInteger(String.valueOf(i)))).add(BigInteger.ONE);
      result = result.add(cur);
    }
    return result;
  }

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