import java.util.Scanner;

public class DanceHall {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        double length = Double.parseDouble(scan.nextLine());
        double width = Double.parseDouble(scan.nextLine());
        double wardrobeSide = Double.parseDouble(scan.nextLine());
        double hallArea = (length * 100) * (width * 100);
        double wardrobeArea = (wardrobeSide*100)*(wardrobeSide*100);
        double bench = hallArea/10;
        double freeArea = hallArea - wardrobeArea - bench;
        double numOfDancers = freeArea/(40+7000);
        System.out.printf("%.0f", numOfDancers);

    }
}