let I() = let a = stdin.ReadLine().Split(' ') |> Array.map int in a.[0], a.[1]
let Aw,Ab = I()
let Bw,Bb = I()
let C,D = I()
let m0 = if C>=Ab then C-Ab else 0
let Bw2 = Bw+m0
let m1 = if Bw2>=D then D else Bw2
printfn "%d" (Aw-m0+m1)