#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  int a, b, x, y;
  cin >> a >> b >> x >> y;
  cout << fixed << setprecision(15) << max(min((double) x / a * b, (double) y) * (a + b) / b, min((double) y / b * a, (double) x) * (a + b) / a) << endl;
  return 0;
}