import java.util.*;
import java.util.stream.*;
class Main {
    static Scanner s=new Scanner(System.in);
    static int gInt(){return Integer.parseInt(s.next());}
    public static void main(String[]$){
        int a=gInt(),b=gInt();
        System.out.println((a+b)*Math.min(s.nextDouble()/a,s.nextDouble()/b));
    }
}