import java.util.*

fun main(args: Array<String>) {
    val scanner = Scanner(System.`in`)
    val k = scanner.nextInt()
    val a = scanner.nextInt()
    val b = scanner.nextInt()
    for(i in a..b){
        if(i%k === 0){
            println("OK")
            return
        }
    }
     println("NG")
}