public class Square {

    static int square(int n){
	if (n==0) return 0;
	else return n + n - 1 + square(n-1);
    }

    public static void main(String[] args) {
	int n = Integer.parseInt(args[0]);
	System.out.println(square(n));
    }
}
//
// Recursive square ... 
// Derived from the bathroom floor
// Only defined for non-negative numbers
//