fun main(args: Array<String>) {
    val t = readLine()!!.toInt()
    val (a, b) = readLine()!!.split(" ").map(String::toInt)
    var isContain = false
    for (i in a..b) {
        if (i % t == 0) {
            isContain = true
            break
        }
    }
    if (isContain) {
        println("OK")
    } else {
        println("NG")
    }
}