fun main() {
    val k = readLine()!!.toInt()
    val ab = readLine()!!.split(" ").map { it.toInt() }
    val a = ab[0]
    val b = ab[1]
    var tmp = k
    while (tmp <= b) {
        if (a <= tmp) {
            println("OK")
            return
        }
        tmp += k
    }

    println("NG")
}

