n, k = gets.split.map(&:to_i)
cs = " #{gets.chomp}"
idxs = cs[k] == "(" ? k.upto(cs.length) : k.downto(1)

count = 0
idxs.each do |idx|
  count += cs[idx] == cs[k] ? +1 : -1
  if count == 0 then
    puts idx
    break
  end
end