#include <stdio.h>
int main (void)
{
	int a,b,x,y;
	double	ad,bd,xd,yd,n;
	scanf("%d %d %d %d",&a,&b,&x,&y);
	ad=a;
	bd=b;
	xd=x;
	yd=y;

	if((x/a)>(y/b))
	{
		n = yd * (ad + bd)/bd;
	}
	else
	{
		n = xd * (ad + bd)/ad;
	}
	printf("%f\n",n);
	return 0;
}