import java.util.Scanner;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;

class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        double a = in.nextDouble();
        double b = in.nextDouble();
        double x = in.nextDouble();
        double y = in.nextDouble();

        System.out.println((a + b) * (Math.min((x/a), (y/b))));

        in.close();
    }
}