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.
x = input()
s, nclosed = [], [0]
max_nbrackets = 0
result_start, result_end = 0, 0
OPEN_BRACKET = {')': '(', ']': '['}

for i, c in enumerate(x):
    if c in (')', ']') and s and OPEN_BRACKET[c] == s[-1][1]:
        index, _ = s.pop()
        if c == ']' and nclosed[-1] + 1 > max_nbrackets:
            result_start, result_end = index, i
            max_nbrackets = nclosed[-1] + 1
        elif c == ')':
            top = nclosed.pop()
            nclosed[-1] += top
        
        if c == ']':
            nclosed[-1] += 1
    elif c in ('(', '['):
        s.append((i, c))
        if c == '(':
            nclosed.append(0)
    else:
        s, nclosed = [], 0

print(max_nbrackets)
if nclosed:
    print(x[result_start:result_end + 1])
	 	        	 	 	 	  		 	   				