open System
type Sol() =
    member this.Solve() = 
        let (A,B) = stdin.ReadLine().Split(' ') |> Array.map int |> fun ss -> (ss.[0], ss.[1])
        let f a b = if a > b then (2000000000 - b - 1) else (b - 2)
        f A B |> printfn "%d"

let mySol = new Sol()
mySol.Solve()