#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
#include<set>
#include<bitset>
#include<math.h>
#include<map>
#include<queue>
#include<iomanip>
using namespace std;

int main(){
    double a, b, x, y, base;
    cin >> a >> b >> x >> y;
    base = (x/a > y/b) ? (a+b)*y/b : (a+b)*x/a;
    cout << fixed << setprecision(7) << base << endl;
}