@x=[];a=[];@t=[]
n,k = gets.chomp.split(" ").map(&:to_i)
@x+=gets.chomp.split(" ").map(&:to_i)
a+=gets.chomp.split(" ").map(&:to_i)
@hash = Hash[*([@x,a].transpose.flatten)]
p=@x[k-1]

def f(p,w)
  b = @hash[p]
  zzz = p+w*b
  zzz1 = p+(-1*w*b)
  @x.each do |elm|
    if zzz1 > zzz
      if elm >=zzz and zzz1 >= elm
        if @t.any? {|w| w == elm }
          next
        else
          @t<<elm
        end
        f(elm,1)
      end
    else
      if zzz >= elm and elm >= zzz1
        if @t.any? {|w| w == elm }
          next
        else
          @t<<elm
        end
        f(elm,1)
      end
    end
  end
end

f(p,1)

if @t==nil
  p "1"
else
  p @t.length
end