open System
type Sol() =
    member this.Solve() = 
        
        let [|N;K|] = stdin.ReadLine().Split() |> Array.map int
        let f n k =
            match (n,k) with
            | (_,1) -> (1 <<< (n-1) ) - n
            | (_,_) -> (1 <<< (n-k) )
        
        f N K |> printfn "%d"
        
let mySol = new Sol()
mySol.Solve()