Hello everybody,

I'm having trouble with the digital_sum exercise of Practice Makes Perfect:

https://www.codecademy.com/courses/python-intermediate-en-rCQKw/0/4?curriculum_id=4f89dab3d788890003000096

I think I already have the answer; however, I keep getting this error message:

Oops, try again. Your function fails on digit_sum(434). It returns None when it should return 11.

Here is my code:

```
n = raw_input('Enter number')
def digit_sum(n):
n = str(n)
s = 0
for i in n:
s = s + int(i)
print s
digit_sum(n)
```

The weird part is that I've tried it with 434 and I do get the desired result of 11. Any help?