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.
# Author Name: Ajay Meena
# Codeforce : https://codeforces.com/profile/majay1638
import sys
import math
import bisect
import heapq
from bisect import bisect_right
from sys import stdin, stdout

# -------------- INPUT FUNCTIONS ------------------


def get_ints_in_variables(): return map(
    int, sys.stdin.readline().strip().split())


def get_int(): return int(sys.stdin.readline())


def get_ints_in_list(): return list(
    map(int, sys.stdin.readline().strip().split()))
def get_list_of_list(n): return [list(
    map(int, sys.stdin.readline().strip().split())) for _ in range(n)]


def get_string(): return sys.stdin.readline().strip()

# -------- SOME CUSTOMIZED FUNCTIONS-----------


def myceil(x, y): return (x + y - 1) // y

# -------------- SOLUTION FUNCTION ------------------


def Solution(s):
    # Write Your Code Here
    s = [c for c in s]
    stk = []
    st = set(range(len(s)))
    for i in range(len(s)):
        if s[i] in "([":
            stk.append([s[i], i])
        else:
            if len(stk):
                if stk[-1][0]+s[i] in "(][)":
                    stk = []
                else:
                    st.remove(i)
                    st.remove(stk[-1][1])
    for i in st:
        s[i] = " "
    s = "".join(s).split()
    ans, cnt = "", 0
    for substr in s:
        k = substr.count("[")
        if k > cnt:
            ans = substr
            cnt = k
    print(cnt)
    print(ans)


def main():
    # Take input Here and Call solution function
    Solution(get_string())


# calling main Function
if __name__ == '__main__':
    main()
