1
class Solution:
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    def isValid(self, code: str) -> bool:
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        if code[0] != "<" or code[-1] != ">":
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            return False
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        i, n = 0, len(code)
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        stk = []
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        while i < n:
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            if code[i] == "<":
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                if i != 0 and code[i : i + 9] == "<![CDATA[":
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                    if not stk:
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                        return False
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                    j = i + 9
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                    while j + 3 <= n and code[j : j + 3] != "]]>":
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                        j += 1
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                    if code[j : j + 3] == "]]>":
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                        i = j + 3
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                    else:
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                        return False
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                else:
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                    start = i
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                    isend = False
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                    i += 1
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                    if i >= n:
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                        return False
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                    if code[i] == r"/":
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                        isend = True
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                        i += 1
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                    if i >= n:
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                        return False
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                    tag = ""
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                    while i < n and code[i] != ">":
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                        if not code[i].isupper():
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                            return False
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                        tag += code[i]
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                        i += 1
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                    if i >= n or len(tag) == 0 or len(tag) > 9:
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                        return False
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                    if isend:
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                        if not stk or stk[-1] != tag:
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                            return False
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                        stk.pop(-1)
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                    else:
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                        if start != 0 and not stk:
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                            return False
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                        stk.append(tag)
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                    i += 1
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            else:
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                if not stk:
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                    return False
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                while i < n and code[i] != "<":
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                    i += 1
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        return not stk