#include<bits/stdc++.h>

using namespace std;
using ll = long long;

int main(){
    double a,b,x,y;
    cin >> a >> b >> x >> y;
    cout << fixed << setprecision(15);

    if(a*y == b*x){
        cout << x + y << endl;
    }else{
        cout << min((a+b)*(x/a),(a+b)*(y/b)) << endl;
    }
    return 0;
}