type Bag = { 
  WhiteStone: int 
  BlackStone: int }

let solve a b c d =
  let c_b = min a.BlackStone c
  let c_w = c - c_b
  let a' = { WhiteStone = a.WhiteStone - c_w; BlackStone = a.BlackStone - c_b }
  let b' = { WhiteStone = b.WhiteStone + c_w; BlackStone = b.BlackStone + c_b }
 
  let d_w = min b'.WhiteStone d 
  let d_b = d - d_w
  // let a'' = { WhiteStone = a'.WhiteStone + d_w; BlackStone = a'.BlackStone + d_b }
  // let b'' ...

  a'.WhiteStone + d_w

let R() = stdin.ReadLine().Split() |> Array.map int

let A = 
  let t = R()
  { WhiteStone = t.[0]; BlackStone = t.[1] }
let B = 
  let t = R()
  { WhiteStone = t.[0]; BlackStone = t.[1] }
let C, D =
  let t = R()
  t.[0], t.[1]

solve A B C D
|> stdout.WriteLine