Given a number, write a function to output its reverse digits.  (e.g. given 123 the answer is 321)
Numbers should preserve their sign; i.e. a negative number should still be negative when reversed.
### Examples
```
 123 ->  321
-456 -> -654
1000 ->    1
```
def reverse_number(n):
  
  if n < 0 :
     a = str(n)[1:]
     return int("{}{}".format(str(n)[0] , a[::-1]))
  else:
     return int(str(n)[::-1])
def reverse_number(n):
  
  if n < 0 :
     a = str(n)[1:]
     return int("{}{}".format(str(n)[0] , a[::-1]))
  else:
     return int(str(n)[::-1])