# encoding: utf-8
 
a = gets.split(' ').map{|n| n.to_i}.to_a
n = a[0]
k = a[1]
s = gets.chomp.split("")
lr = s.at(k-1)
 
if lr == ")"
  s = s.reverse
  k = n - k
  f = true
else
  k -= 1
end
i = 1
 
while k <= n do
  k += 1
  if s.at(k) == lr
    i += 1
  else
    i -= 1
    if i == 0
      if f
      	puts n-k
      else
      	puts k+1
      end
      break
    end
  end
end
if k == n
	puts "no"
end