package main

import "bufio"
import "fmt"
import "os"
import "strconv"

func min(a int, b int) int {
	if a < b {
		return a
	} else {
		return b
	}
}
func max(a int, b int) int {
	if a < b {
		return b
	} else {
		return a
	}
}

func main() {
	var scanner = bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)
	var nextInt = func() int {
		scanner.Scan()
		n, _ := strconv.Atoi(scanner.Text())
		return n
	}

	var n = nextInt()
	var k = nextInt() - 1
	var x = make([]int, n)
	for i := 0; i < n; i++ {
		x[i] = nextInt()
	}
	var a = make([]int, n)
	for i := 0; i < n; i++ {
		a[i] = nextInt()
	}

	var i = k
	var j = k
	var l = x[k] - a[k]
	var r = x[k] + a[k]
	var updated = true
	for updated {
		updated = false
		for i-1 >= 0 && l <= x[i-1] {
			l = min(l, x[i-1]-a[i-1])
			r = max(r, x[i-1]+a[i-1])
			i--
			updated = true
		}
		for j+1 < n && x[j+1] <= r {
			l = min(l, x[j+1]-a[j+1])
			r = max(r, x[j+1]+a[j+1])
			j++
			updated = true
		}
	}

	fmt.Println(j - i + 1)
}