func readInts() -> [Int] {
    return readLine()!.split(separator: " ").map { Int($0)! }
}

func main() {
    let k = Int(readLine()!)!
    let line = readInts()
    let a = line[0]
    let b = line[1]
    
    for i in 1...1000 {
        if a <= i * k && i * k <= b {
            print("OK")
            return
        }
    }
    print("NG")
}

main()
