n, k = gets.split.map(&:to_i)
s = gets.chomp.split(//)
count = 1
case s[k-1]
when '('
  k.upto(n-1) do |i|
    count += (s[i] == '(' ? 1 : -1)
    if count == 0
      p i+1
      break
    end
  end
when ')'
  (k-2).downto(0) do |i|
    count += (s[i] == ')' ? 1 : -1)
    if count == 0
      p i+1
      break
    end
  end
end