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

public class Solution {

    static long sumOfGroup(int k) {
        long suma =0;
       for(int i = k-1;i>0;i--){
           suma = suma+k;
       }
        suma = suma + 1;
        //System.out.println(suma);
        long total = 0;
       for(int j = 0;j<k;j++){
           total = total + suma;
           suma = suma + 2;
       }
        return total;
    }

    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();
    }
}