fun main(args: Array<String>) {
    val k = readLine()!!.toInt()
    val range = readLine()!!.split(" ").map { it.toInt() }
    val a = range[0] // min
    val b = range[1] // max

    if(k > b) {
        print("NG")
        return
    }

    if(a%k == 0 || b%k ==0) {
        print("OK")
        return
    }

    var minMultiplyNumber = if(a%k == 0)  a/k else (a/k) + 1
    val maxMultipleNumber = if(b%k == 0)  b/k else (b/k)

    val result = IntRange(minMultiplyNumber * k , maxMultipleNumber * k).firstOrNull{it % k == 0}
    if(result != null) print("OK") else print("NG")
}
