class Calc0022
  def initialize(args)
    args = args.map { |l| l.chomp.split(/\s+/) }
    @n, @k = args.shift.map(&:to_i)
    @s = args.shift.first
  end

  def run
    cs = @s.split(//).map { |c| c == '(' ? 1 : -1 }
    if cs[@k - 1] == 1
      find(cs[(@k - 1)..-1]) + @k
    else
      @k - find(cs[0..(@k - 1)].reverse)
    end
  end

  def find(cs)
    s = 0
    cs.each_with_index do |c, i|
      s += c
      return i if s == 0
    end
  end
end

puts Calc0022.new(STDIN.readlines).run if __FILE__ == $0