import java.util.Scanner;
public class MyClass {
    public static void main(String args[]) {
       Scanner scanner = new Scanner(System.in);
        int num = Integer.parseInt(scanner.nextLine());
        int sum = 0;
        int startNumber = 1;
        for (int i = 1; i <=num; i++) {
            sum+=startNumber;
            startNumber+=2;
        }
        System.out.printf("Sum: %d",sum);
    }
}