scan = string.gmatch(io.read(),"%d+")
n = scan() - 0
k = scan() - 0
s = io.read()
s = {s:byte(1,s.len(s))}
l = string.byte("(")
r = string.byte(")")
result = 0
b = {}
for i = 1, n do
  if s[i] == l then
    table.insert(b,i)
  elseif s[i] == r then
    local pop = table.remove(b)
    if k == pop then
      result = i
      break
    elseif k == i then
      result = pop
      break
    end
  end
end
print(result)