import java.util.Scanner;

public class Dance {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        double length = Double.parseDouble(scanner.nextLine());
        double width = Double.parseDouble(scanner.nextLine());
        double side = Double.parseDouble(scanner.nextLine());

        double hall = (length * 100) * (width * 100);
        double wardrobe = (side * 100) + (side * 100);
        double bench = hall / 10;
        double freeSpace = hall - wardrobe - bench;
        double dancers = freeSpace / (40 + 7000);

        System.out.printf("%.0f" , Math.floor(dancers));
    }
}