import           Control.Monad
import           Control.Monad.ST
import qualified Data.Array                  as A
import qualified Data.Array.ST               as ST
import qualified Data.Array.Unboxed          as AU
import qualified Data.ByteString.Char8       as BS
import           Data.Char
import           Data.Int
import qualified Data.IntMap                 as IM
import           Data.List
import qualified Data.Map                    as M
import           Data.Maybe
import           Data.Ord
import qualified Data.Set                    as S
import           Data.Time
import qualified Data.Vector                 as V
import qualified Data.Vector.Mutable         as VM
import qualified Data.Vector.Unboxed         as VU
import qualified Data.Vector.Unboxed.Mutable as VUM

readInt :: IO [Int]
readInt = map (fst . fromJust . BS.readInt) . BS.words <$> BS.getLine

readInts :: Int -> IO [[Int]]
readInts n = replicateM n readInt

readString :: IO [String]
readString = map BS.unpack . BS.words <$> BS.getLine

readStrings :: Int -> IO [[String]]
readStrings n = replicateM n <$> readString

toPair :: [a] -> (a, a)
toPair [x, y] = (x, y)

main = do
  [n, k] <- readInt
  a <- readInt
  print $ solve n k a

solve n k a = b' + c'
  where
    b = takeWhile (/= 1) a
    c = tail $ dropWhile (/= 1) a
    b' = m (length b) (k - 1)
    c' = m (length c) (k - 1)

m a x
  | a `mod` x == 0 = a `div` x
  | otherwise = a `div` x + 1
