def f(s, n)
  # p [s,n]
  return s.size - f(s.reverse.tr("()",")("), s.size - n - 1) - 1if s[n] == ?)

  i = n
  g = lambda{|depth|
    return i if depth < 0
    i += 1
    if s[i] == ?(
      g.(depth+1)
    else
      g.(depth-1)
    end
  }
  g.(0)
end

N, K = gets.split.take(2).map(&:to_i)
S = gets[0,N]

p f(S, K-1) + 1