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

int main(){
	double A,B,X,Y;
	cin >> A >> B >> X >> Y;
	
	
	double ans1 = 0 , ans2 = 0;
	if( Y >= B/A*X - 1e-9) ans1 = X + B/A*X;
	if( X >= A/B*Y - 1e-9) ans2 = Y + A/B*Y;
	
	printf("%.10lf\n",max(ans1,ans2));
	
	
}