import qualified Data.Text as T
import qualified Data.Text.IO as T
import qualified Data.Text.Read as T

main :: IO ()
main = do
  k <- unsafeTextToInt <$> T.getLine :: IO Int
  [a, b] <- map unsafeTextToInt . T.words <$> T.getLine :: IO [Int]
  let
    q = b `div` k :: Int
  putStrLn $ if a <= k * q then "OK" else "NG"

unsafeTextToInt :: T.Text -> Int
unsafeTextToInt s = case T.signed T.decimal s of
  Right (n, _) -> n
