number_string=str(input()) number=int(number_string) n=number.split(',') print(max(n))

There are a few issues with the code provided. Here is a corrected version:

number_string = input() # no need to use str() since input() already returns a string
n = number_string.split(',') # split the string using the comma as separator
n = [int(x) for x in n] # convert each element to an integer
print(max(n)) # print the maximum value

This code first reads a string from the user input, splits it into a list of strings using the comma as separator, converts each string to an integer, and then finds the maximum value in the list using the `max()` function.

Note that the `split()` method returns a list of strings, so we need to convert each string to an integer before we can find the maximum value. This is done using a list comprehension, which creates a new list by applying a function (in this case, `int()`) to each element of an existing list.