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

public class Solution {

    static long sumOfGroup(long k) {
    long first = (k*k) - k +1;
    long temp = first;
    long sum = 0;    
    for(int i=1;i<=k;i++){
    sum+=temp;
    temp+=2;    
    }
    return sum;    
    }

    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();
    }
}