package Exams.Nov_2018;

        import java.util.Scanner;

public class I_02WeddingHall {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double length=Integer.parseInt(scanner.nextLine());
        double width=Integer.parseInt(scanner.nextLine());
        double barSide=Integer.parseInt(scanner.nextLine());

        double hallArea=length*width;
        double dancing=hallArea*0.19;

        double freeSpace=hallArea-barSide*barSide-dancing;
        double dancerCount=Math.ceil(freeSpace/3.2);


        System.out.printf("%.0f",dancerCount);

    }
}