fun main() {
    val k = readLine()!!.toInt()
    val input = readLine()!!.split(" ")
    val a = input[0].toInt()
    val b = input[1].toInt()
    var result = "NG"
    var i = k

    run loop@{
        while (i <= b) {
            if (i in a..b) {
                result = "OK"
                return@loop
            }
            i += k
        }
    }
    println(result)
}