{-# LANGUAGE PartialTypeSignatures #-}
module Main (main) where
 
import qualified Data.ByteString.Char8 as C8
import Data.Bool
import qualified Data.Char as C
import qualified Data.List as L
 
main :: IO ()
main = do
  [k] <- readInts
  readInts >>= output . solve k
 
solve :: Int -> [Int] -> _
solve k [a,b]
  | k == 1 = True
  | (b-a) <= k = not $ null $ filter (\v -> v `mod` k == 0) $ [a..b]
  | otherwise = k <= b-a
 
output :: _ -> IO ()
output = putStrLn . bool "NG" "OK"
 
-- utils
readInts :: IO [Int]
readInts = L.unfoldr (C8.readInt . C8.dropWhile C.isSpace) <$> C8.getLine