object Main extends App {
  import io.StdIn._
  
  val k = readInt()
  val Array(a, b) =
    readLine()
      .split(" ")
      .map(_.toInt)
    
  var m = a
  var pass = false
  while (m < b && !pass) {
    if (m % k == 0)
      pass = true

    m += 1
  }

  println {
    if (pass) "OK"
    else "NO"
  }
}