#include <bits/stdc++.h>
using namespace std;

int main(){
	int A,B,X,Y;
	cin>>A>>B>>X>>Y;
	double ans=0;
	if(Y>=(double)X*B/A) ans=(double)X*B/A+X;
	if(X>=(double)Y*A/B) ans=max<double>(ans,(double)Y*A/B+Y);
	printf("%.7lf",ans);
	return 0;
}