import kotlin.math.max
import kotlin.math.min

// なんか本番でエラーでる
private val isDebug = runCatching {
  System.getenv("MY_DEBUG") != null
}.fold({it}, {false})

private fun readLn() = readLine()!!
private fun readInt() = readLn().toInt()
private fun readStrings() = readLn().split(" ")
private fun readInts() = readStrings().map { it.toInt() }.toIntArray()
private fun readLongs() = readStrings().map { it.toLong() }.toLongArray()
private fun debug(msg: () -> String) {
  if (isDebug) System.err.println(msg())
}
private fun debug(a: LongArray) {
  if (isDebug) debug{a.joinToString(" ")}
}

val MOD = 1000000007

data class Entry(val i: Int, val x: Long)

fun main() {
  var (N, K) = readInts()
  K--
  val X = readLongs()
  val A = readLongs()
  val set = java.util.TreeSet<Entry>(Comparator<Entry> { o1, o2 ->
    o1.x.compareTo(o2.x)
  })
  for (i in 0 until N) {
    set.add(Entry(i, X[i]))
  }

  var ans = 0
  var l = X[K]
  var r = X[K]
  while(true) {
    val e1 = set.higher(Entry(-1, l - 1))
    val e2 = set.lower(Entry(-1, r + 1))
    debug{"l:$l r:$r"}
    if (e1 != null && e2 != null && e1.x <= e2.x) {
      set.remove(e1)
      l = min(l, e1.x - A[e1.i])
      r = max(r, e1.x + A[e1.i])
      ans++
    } else {
      break
    }
  }

  println(ans)
}