@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 aaa(elm)
 if @t.any? {|w| w == elm }
   return true
 else
   @t.push(elm)
 end
end

update = true
while(update)
  b = @hash[p]
  zzz = p+b
  zzz1 = p+(-1*b)
  @x.each do |elm|
    if zzz1 > zzz
      if elm >=zzz and zzz1 >= elm
        next if aaa(elm)== true
        p = elm
        break
      elsif @x.last == elm
        update = false
      end

    else
      if zzz >= elm and elm >= zzz1
        next if aaa(elm)== true
        p = elm
        break
      elsif @x.last == elm
        update = false
      end
    end
  end
end

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