import java.util.*

fun main() {
    val sc = Scanner(System.`in`)
    var k: Int = sc.nextInt()
    var a: Int = sc.nextInt()
    var b: Int = sc.nextInt()
    var i = k
    while (i <= b) {
        if (i in a..b) {
            println("OK")
            return
        }
        i += k
    }
    println("NG")
}
