#include<iostream>
#include<stdio.h>

using namespace std;

int main(){

    int a, b, x, y;
    cin>> a>> b>> x>> y;

    int mn;
    double r;
    if(a*y > b*x){
        mn = x;
        r = (double)b/a;
    }else{
        mn = y;
        r = (double)a/b;
    }

    printf("%.14f\n", mn+mn*r);

    return 0;
}