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

public class Solution {

    static long sumOfGroup(int n) {
        // Return the sum of the elements of the k'th group.
        //if(n == 0) System.out.println(1);
        long sum = 0;
        long aux = sumation(n) + 1;
        for(long i = aux; i < aux + n;i++){
            sum += oddNumber(i);
        }
        return sum;
    }
    static long sumation (long n){
        return (n*(n-1))/2;
    }
    static long oddNumber(long n){
        return 2*n-1;
    }

    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();
    }
}