ceildiv x y = div (x + y - 1) y

main = do
    k <- readLn :: IO Int
    [a, b] <- map read . words <$> getLine :: IO [Int]
    let x0 = k * ceildiv a k
    let x1 = k * div b k
    putStrLn $ if x0 <= x1 then "OK" else "NG"
