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

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