n, k = gets.split(' ').map(&:to_i)
s = gets.chomp

i = 0
pre_c = ''
a = s.chars.map do |c|
  if c == '(' && pre_c != ')'
    i += 1
  elsif c == ')' && pre_c != '('
    i -= 1
  end
  pre_c = c
  i
end

if (s[k - 1] == '(')
  f = k
  t = n - 1
  m = :upto
else
  f = k - 2
  t = 0
  m = :downto
end

f.send(m, t) do |i|
  if a[k - 1] == a[i]
    puts i + 1
    exit
  end
end