{-# OPTIONS_GHC -O2 #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE Strict #-}
{-# LANGUAGE StrictData #-}
import qualified Data.Vector.Unboxed as VU
import qualified Data.Vector.Unboxed.Mutable as VUM
import Data.Array.Unboxed
import Data.Array.ST
import qualified Data.ByteString.Char8 as BS
import Control.Monad
import Data.List
import Data.Char

main :: IO ()
main = do
    k <- readLn
    (a,b) <- (\vec -> (vec VU.! 0, vec VU.! 1)) . VU.unfoldrN 2 (BS.readInt . BS.dropWhile isSpace) <$> BS.getLine
    let q = a `div` k
    putStrLn $ if k*(q+1) <= b || a `mod` k == 0 then "OK" else "NG"