import re, functools
string = "123454321"
n = 4
res = max([functools.reduce(lambda x, y: int(x) * int(y), num) for num in re.findall(r'(?=(\d{4}))', string)])
print(res)
aW1wb3J0IHJlLCBmdW5jdG9vbHMKc3RyaW5nID0gIjEyMzQ1NDMyMSIKbiA9IDQKcmVzID0gbWF4KFtmdW5jdG9vbHMucmVkdWNlKGxhbWJkYSB4LCB5OiBpbnQoeCkgKiBpbnQoeSksIG51bSkgZm9yIG51bSBpbiByZS5maW5kYWxsKHInKD89KFxkezR9KSknLCBzdHJpbmcpXSkKcHJpbnQocmVzKQ==