func main()
	var n: int :: cui@inputInt()
	var k: int :: cui@inputInt()
	var x: []int :: #[n]int
	var a: []int :: #[n]int
	for i(0, n - 1)
		do x[i] :: cui@inputInt()
	end for
	for i(0, n - 1)
		do a[i] :: cui@inputInt()
	end for
	
	var l: int :: k - 2
	var r: int :: k
	var xl: int :: x[k - 1] - a[k - 1]
	var xr: int :: x[k - 1] + a[k - 1]
	
	while loop(true)
		if(l >= 0 & x[l] >= xl)
			do xl :: [xl, x[l] - a[l]].min()
			do xr :: [xr, x[l] + a[l]].max()
			do l :- 1
			do ans :+ 1
			skip loop
		end if
		if(r < n & x[r] <= xr)
			do xl :: [xl, x[r] - a[r]].min()
			do xr :: [xr, x[r] + a[r]].max()
			do r :+ 1
			do ans :+ 1
			skip loop
		end if
		break loop
	end while
	
	var ans: int :: r - l - 1
	do cui@print("\{ans}\n")
end func