let () =
  let a, b, c, d = Scanf.scanf "%d %d %d %d\n" (fun a b c d -> a, b, c, d) in
  let d' = d / (c+1) in
  let b' = d' * c in
  Printf.printf "%d\n"
    (if a >= d' && b >= b' then d' else if b >= b' then a else b / c)