import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int A = sc.nextInt();
        int B = sc.nextInt();
        int X = sc.nextInt();
        int Y = sc.nextInt();
        double c = (double)X/A;
        double d = (double)Y/B;
        double e = Math.min(c,d);
        double r = e*(A+B);
        System.out.println(r);
    }
}