import java.util.Scanner

object Problem274 {

  def proc(row: Int, col: Int, fromTo: Seq[(Int, Int)]): String = {
    val m = new collection.mutable.HashMap[Int, Int]()
    for (i <- 0 until col) {
      m += i -> 0
    }

    fromTo foreach { case (from, to) =>
      for (i <- from to to) {
        m(i) += 1
      }
      val oppositeFrom = col - 1 - to
      val oppositeTo = col - 1 - from
      for (i <- oppositeFrom to oppositeTo) {
        m(i) += 1
      }
    }

    if (m.forall(_._2 <= 2)) "YES" else "NO"
  }

  def main(args: Array[String]) {
    val sc = new Scanner(System.in)
    val n = sc.nextInt()
    val m = sc.nextInt()
    val fromTo = Seq.fill(n)(sc.nextInt(), sc.nextInt())

    val result = proc(n, m, fromTo)
    println(result)
  }
}