Oops, try again. Does your digit_sum function take exactly one argument (a positive integer)? Your code threw a "'int' object is not iterable" error.

My code can meet the function requirement and output the right answer. Just don't why always showed error.

```
def digit_sum(n):
m=[]
for i in n:
i=int(i)
m.append(i)
print m
return sum(m)
n=raw_input("positive number: ")
print digit_sum(n)
```