//https://ncode.syosetu.com/n4830bu/236/
#include <bits/stdc++.h>
using namespace std;

int main() {
    double A, B, X, Y;
    cin >> A >> B >> X >> Y;
    cout << fixed << setprecision(10) << min(X / A, Y / B) * (A + B) << endl;
}