#include <bits/stdc++.h>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;

int main(){
	int a, b, x, y;
	cin >> a >> b >> x >> y;
	double t=min((double)x/a, (double)y/b);
	printf("%.9f\n", (a+b)*t);
	return 0;
}