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.
def bracket_seq(s):
	n = len(s)
	stack = []
	stack_index = []
	mark = [0]*n
	for i in range(n):
		if s[i] in ['(', '[']:
			stack.append(s[i])
			stack_index.append(i)
		else:
			if len(stack) != 0:
				if stack[-1] == '[' and s[i] == ']':
					mark[i] = 1
					mark[stack_index[-1]] = 1
				elif stack[-1] == '(' and s[i] == ')':
					mark[i] = 1
					mark[stack_index[-1]] = 1
				del stack[-1]
				del stack_index[-1]
	#print(mark)
	max_val = 0
	cur_val = 0
	max_substring = []
	cur_substring = []
	for i in range(n):
		if mark[i] == 1:
			if s[i] == '[':
				cur_val += 1
			cur_substring.append(s[i])
			if cur_val>max_val:
				max_val = cur_val
				max_substring = cur_substring
		else:
			cur_substring = []
			cur_val = 0

	return max_val, max_substring



s = input()
n, result = bracket_seq(s)

if n==0:
	print(0)
else:
	print(n)
	print(result)