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.
st = []
start = 0
end = 0
ans = 0
best = ''
i = 0

str = input()

while i < len(str):
    if str[i] in ['(','[']:
        st.append(str[i])
    else:
        if str[i] == ')':
            if len(st) and st[-1] == '(':
                st.pop()
                if len(st) == 0:
                    end = i
                    if str[start:end+1].count('[') > ans:
                        ans = str[start:end+1].count('[')
                        best = str[start:end+1]

            elif len(st) and st[-1] == '[':
                start += 1
                st.pop()
            else:
                start = i + 1
                end = i + 1

        elif str[i] == ']':
            if len(st) and st[-1] == '[':
                st.pop()
                if len(st) == 0:
                    end = i
                    if str[start:end+1].count('[') > ans:
                        ans = str[start:end+1].count('[')
                        best = str[start:end+1]

            elif len(st) and st[-1] == '(':
                start += 1
                st.pop()
            
            else:
                start = i + 1
                end = i + 1

    if i == len(str) - 1 and len(st) != 0:
        i = start
        start = i + 1
        end = i + 1
        # print(start)
        # print(end)
        st = []

    i += 1


print(ans)
print(best)


                
