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

public class Solution {

    static long sumOfGroup2(int k) {
        // Return the sum of the elements of the k'th group.
        
        long multiply=k*(k-1);
        long current=((multiply/2) +1)*2-1;
        long sum=0;
        for(long i=0;i<k;i++){
            sum+=current;
            current=current+2;
        }
        return sum;
    }
    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        BigInteger big_k=BigInteger.valueOf(k);
        BigInteger multiply=big_k.multiply(big_k.subtract(BigInteger.valueOf(1)));
        BigInteger current=multiply.divide(BigInteger.valueOf(2)).add(BigInteger.valueOf(1)).multiply(BigInteger.valueOf(2)).subtract(BigInteger.valueOf(1));
        BigInteger sum=BigInteger.valueOf(0);
        for(long i=0;i<k;i++){
            sum=sum.add(current);
            current=current.add(BigInteger.valueOf(2));
        }
        return sum.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();
    }
}