import java.util.Scanner;

public class DanceHall {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double lenght = Double.parseDouble(scan.nextLine());
        double weight = Double.parseDouble(scan.nextLine());
        double sideA = Double.parseDouble(scan.nextLine()); //wardrobe

        double areaHall = (lenght * 100) * (weight * 100); // m3 to sm3
        double bench = areaHall / 10;
        double areaA = (sideA * 100) * (sideA * 100); //wardrobe
        double freeSpace = areaHall - bench - areaA;

        double dancers = freeSpace / (40 + 7000);
        int result = (int)Math.round(dancers); //from double to int
        System.out.println(result);
    }
}