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

signed main(){
  int A, B, X, Y; cin >> A >> B >> X >> Y;
  double k = min( 1.0 * X / A, 1.0 * Y / B );
  cout << fixed << setprecision( 7 ) << k * ( A + B ) << endl;
  return 0;
}