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

int main()
{
	double a, b, x, y;
	scanf("%lf %lf %lf %lf", &a, &b, &x, &y);
	x = min(x, y * a / b);
	y = min(y, x * b / a);
	printf("%.20f\n", x + y);
}