fun main(args: Array<String>) {
	val k = readLine()!!.toInt()
  	val (a, b) = readLine()!!.split(" ").map(String::toInt)
  	var i = 0
  	var flg = 0
  
  	val count = 1000 / k
  
  	for (i in 0..count) {
     	val len = i * k
      	if(len >= a && len <= b) {
        	print("OK")
          	flg = 1
          	break;
        }
    }
  	if (flg == 0) {
     	print("NG") 
    }
}