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.
s = input()
st = []
prans = 0
ans = 0
maxst = []
lenn = 0
for i in range(len(s)):
    if i == 280:
        print(st)
    if s[i] == "(":
        st.append(s[i])
    elif s[i] == "[":
        st.append(s[i])
    else:
        if st and s[i] == "]" and st[-1] == "[":
            lenn += 1
            prans += 1
            st.pop()
        elif st and s[i] == "(" and st[-1] == ")":
            lenn += 1
            st.pop()
        elif st and ((s[i] == "]" and st[-1] == "(") or (s[i] == ")" and st[-1] == "[")):
            prans = 0
            lenn = 0
            st = []
        elif not st and (s[i] == "]" or s[i] == ")"):
            prans = 0
            lenn = 0
            st = []
        if prans > ans:
            anss = s[i - lenn * 2 + 1: i + 1]
            stt = []
            for j in anss:
                if j == "(" or j == "[":
                    stt.append(j)
                elif not stt:
                    break
                elif j == "]" and stt[-1] == "[":
                    stt.pop()
                elif j == ")" and stt[-1] == "(":
                    stt.pop()
                else:
                    break
            else:
                if not stt:
                    ans = prans
                    maxst = s[i - lenn * 2 + 1: i + 1]
print(ans)
for i in maxst:
    print(i, end='')
