#include <bits/stdc++.h>
using namespace std;

int main(){
    int A, B, X, Y;
    double diviAB, diviBA;

    cin >> A >> B >> X >> Y;
    diviAB = (double)A/B;
    diviBA = (double)B/A;

    if(A == B){
        if(X <= Y){
            cout << 2*X << endl;
        }else{
            cout << 2*Y << endl;
        }
        return 0;
    }else if(A*Y >= X*B){
        //cout << X + diviBA*X << endl;
        printf("%.7f\n", X + diviBA*X);
    }else{
        //cout << Y + diviAB*Y << endl;
        printf("%.7f\n", Y + diviAB*Y);
    }
    return 0;

}