s = gets.split
n = s[0].to_i
k = s[1].to_i
stack = 0
str = gets
a = Array.new
if str[k - 1] == "("
    (k - 1).upto(n - 1) do |i|
        if str[i] == "("
            stack += 1
        else
            stack -= 1
        end
        if stack == 0
            puts i + 1
            break
        end
    end
else
    (k - 1).downto(0) do |i|
        if str[i] == ")"
            stack += 1
        else
            stack -= 1
        end
        if stack == 0
            puts i + 1
            break
        end
    end
end