@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)
  p=@x[k-1]

  update = true
  @t=[nil]
  xxx = @x.length

  def aaa(elm)
    if @t.any? {|w| w == elm }
      return true
    else
      @t.compact!
      @t<<elm
      return false
    end
  end

  while(update)
    if @t[0]==nil
      b = a[k-1]
      zzz = p+b
      zzz1 = p+(-1*b)
      for i in 0...xxx do
        if zzz1 > zzz
          if @x[i] >=zzz and zzz1 >= @x[i]
            break if aaa(@x[i])==false
          end
        else
          if zzz >= @x[i] and @x[i] >= zzz1
            break if aaa(@x[i])==false
          end
        end
        break if i == xxx-1
      end
    else
      @t.each do |elm|
        j = @x.find_index{|n|n%elm==0}
        b = a[j]
        zzz = elm+b
        zzz1 = elm+(-1*b)
        for i in 0...xxx do
          update = false if i == xxx-1
          if zzz1 > zzz
            if @x[i] >=zzz and zzz1 >= @x[i]
              aaa(@x[i])
            end
          else
            if zzz >= @x[i] and @x[i] >= zzz1
              aaa(@x[i])
            end
          end
        end
      end
    end
  end
if @t==nil
 p "1"
else
 p @t.length
end