A bracket sequence is a string, containing only characters "(", ")", "[" and "]".

A correct bracket sequence is a bracket sequence that can be transformed into a correct arithmetic expression by inserting characters "1" and "+" between the original characters of the sequence. For example, bracket sequences "()[]", "([])" are correct (the resulting expressions are: "(1)+[1]", "([1+1]+1)"), and "](" and "[" are not. The empty string is a correct bracket sequence by definition.

A substring *s*[*l*... *r*] (1 ≤ *l* ≤ *r* ≤ |*s*|) of string *s* = *s*<sub class="lower-index">1</sub>*s*<sub class="lower-index">2</sub>... *s*<sub class="lower-index">|*s*|</sub> (where |*s*| is the length of string *s*) is the string *s*<sub class="lower-index">*l*</sub>*s*<sub class="lower-index">*l* + 1</sub>... *s*<sub class="lower-index">*r*</sub>. The empty string is a substring of any string by definition.

You are given a bracket sequence, not necessarily correct. Find its substring which is a correct bracket sequence and contains as many opening square brackets «[» as possible.
The first and the only line contains the bracket sequence as a string, consisting only of characters "(", ")", "[" and "]". It is guaranteed that the string is non-empty and its length doesn't exceed 10<sup class="upper-index">5</sup> characters.
'''input
(((())))[
'''
from sys import stdin


def merge(index):
	aux = []
	if len(index) > 0:
		aux = [[index[0][0], index[0][1]]]
		for i in range(1, len(index)):
			if index[i][0] == aux[-1][1] + 1:
				aux[-1][1] = index[i][1]
			else:
				aux.append(index[i])
	return aux


# main starts
string = stdin.readline().strip()
stack = []
index = []
start = -1
end = -1
for i in range(len(string)):
	if len(stack) == 0:
		# appeding the substring
		if start != -1:
			index.append([start, end])

		# setting new start
		start = i
		end = i

	if string[i] in ['(', '[']:
		stack.append(string[i])
	elif string[i] == ')':
		if len(stack) > 0 and stack[-1] == '(':
			stack.pop()
		else:
			stack = []
			start = -1
			end = -1
			continue
	elif string[i] == ']':
		if len(stack) > 0 and stack[-1] == '[':
			stack.pop()
		else:
			stack = []
			start = -1
			end = -1
			continue

	if len(stack) == 0:
		end = i


if len(stack) == 0:
	# appeding the substring
	if start != -1:
		index.append([start, end])


# print(index)
index = merge(index)
# print(index)
# getting the maximum
diff = 0
ans = [-1, -1]
for i in index:
	start, end = i
	if diff < end - start + 1 and '[' in string[start: end + 1] :
		ans = [start, end + 1]
		diff = end - start + 1

print(diff)
print(string[ans[0]: ans[1]])

