Here is what i wrote:

```
number = raw_input('Enter an integer= ')
if number < 0:
    print 'Invalid number'

else:
    for k in range(1,(number)):
        number *= k

print number

```

I want to be able to input any number (that is greater than 0), but when i input a number say 4 (the factorial of 4 is 24) i get this error: 

```
Traceback (most recent call last):
  File "problem.py", line 6, in <module>
    for k in range(1,(number)):
TypeError: range() integer end argument expected, got str.

```

I don't understand what it means and as far as i know the code should be working, Please Help!