package m.shin;
import java.util.Scanner;
public class Con445 {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int a = s.nextInt();
		double b = s.nextDouble();
		s.close();

		double c = (50 * (double)a) / (0.8 + 0.2 * b);
		System.out.println(50 * a + (int)c);
	}

}