I want to find the highest number using import re .txt

I want to be able to just search for all digits in a text file and find the max number, using the re module. Where do I need to edit my code to accomplish this goal? The random.txt looks somthing like the following: Datq15UxkNwMN5zUQhd46J8WeF9RjAq214TlJiQ8EkZvmdOpmBOdd365mICKC67GGvqwbLqV2Gox3n3E5WC1Vq8C22lZ6sL3Ip24untQyw46g2219WlA07GP30PNvc8o3hCb2d283l68mh86RH6gDNbN7kIXmdO4a84hUz73905o3BlR71YCQF985JTz54FRoN32pM8N23YcYd7jv9Ys575UzaH9RZ7sosMdeqnTgnVt0bH99b2P5ilvJ33QaJ6G76VU8vPN

import re
with open('content.txt', 'r',) as f:
    contents = f.read()

    number = 0
    pattern = re.compile(r'\d')
    matches = pattern.finditer('content.txt')
    for match in matches:
        n = int(match)
        if saved <= n:
            number = int(match)
    print(number)

the file just ran once and gave me the answer 0