import Data.List
import Control.Monad

main = getLine >>= print . nasort . map read . words

nasort [n,k] = length $ do
 h3 <- delete [] (subsequences [1..n])
 guard (head h3 == k)
 let as = h3 ++ ([1..n] \\ h3)
 guard (as /= sort as)
 return as