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

public class Solution {

    static long sumOfGroup(long k) {
        // Return the sum of the elements of the k'th group.
         // Return the sum of the elements of the k'th group.
        long startNum=((k-1)*(k))+1;
        long result=startNum;
        
        for(long i=1;i<k;i++){
            startNum+=2;
            result=result+startNum;
        }
        
        return result;
    }

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