n,i = gets.split.map(&:to_i)
s = gets.chomp
stack = []
counter = 0
q = s.chars.map { |v|
    if v == '('
        counter.incr!
        stack.push(counter)
        counter
    else
        -1 * stack.pop
    end
}
half = q[i - 1]
puts q.find_index(-half) + 1