#include<iostream>
#include<stdio.h>
using namespace std;
int main(){
    int a,b,x,y;
    double coffe,tea;
    cin >> a >> b >> x >> y;
    coffe = (double)x/a;
    tea = (double)y/b;
    if(coffe>tea)printf("%.12f\n",tea*(a+b));
    else printf("%.12f\n",coffe*(a+b));
}