n, k = gets.split.map(&:to_i)
s = gets.chomp
stack = []
s.each_char.with_index do |c, i|
  case c
  when '('
    stack << i
  when ')'
    if i == k - 1
      puts stack[-1] + 1
      break
    elsif stack[-1] == k - 1
      puts i + 1
      break
    else
      stack.pop
    end
  end
end