Vegetables

import java.util.Scanner;

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

        double kgv =Double.parseDouble(scanner.nextLine());
        double kgf =Double.parseDouble(scanner.nextLine());
        int totalkgv =Integer.parseInt(scanner.nextLine());
        int totalkgf =Integer.parseInt(scanner.nextLine());

        System.out.println((kgv * totalkgv + kgf * totalkgf) / 1.94);
    }
}