{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE GADTs #-}

-- Control
--import Control.Functor
import Control.Applicative
import Control.Monad
import Control.Monad.ST
import Control.Arrow
--import Control.Category


-- Data
import qualified Data.List as L
-- import qualified Data.Set as S
-- import qualified Data.IntSet as IS
-- import qualified Data.Map as M
-- import qualified Data.IntMap as IM
-- import qualified Data.Sequence as Seq
-- import qualified Data.Tree as Tree
-- import qualified Data.Graph as G
-- import qualified Data.Tuple as Tup
-- import qualified Data.Array as Ary
--import qualified Data.Vector as Vec

import Data.Bool
import Data.Char
import Data.Monoid 
import Data.Ord
import Data.Maybe
import Data.Bits
import Data.Either
import Data.Eq
import Data.Function


-- Debug
import qualified Debug.Trace as DT


-- io
import Text.Printf


main ::IO()
main = do
  [n,k] <- map read . words <$> getLine :: IO [Int]
  putStrLn $ show $ solve n k

solve :: Int -> Int -> Int
solve n 1 = 0
solve n k = n - k
