Jamie is a programmer, and James' girlfriend. She likes diamonds, and wants a diamond string from James. Since James doesn't know how to make this happen, he needs your help.
## Task
You need to return a string that looks like a diamond shape when printed on the screen, using asterisk (`*`) characters. Trailing spaces should be removed, and every line must be terminated with a newline character (`\n`).
Return `null/nil/None/...` if the input is an even number or negative, as it is not possible to print a diamond of even or negative size.
## Examples
A size 3 diamond:
```
 *
***
 *
```
...which would appear as a string of `" *\n***\n *\n"`
A size 5 diamond:
```
  *
 ***
*****
 ***
  *
```
...that is: `"  *\n ***\n*****\n ***\n  *\n"`
def diamond(n):
    if n < 0 or n % 2 == 0:
        return None
    
    result = "*" * n + "\n";
    spaces = 1;
    n = n - 2
    while n > 0:
        current = " " * spaces + "*" * n + "\n"
        spaces = spaces + 1
        n = n - 2
        result = current + result + current
    
    return result
def diamond(n):
    if n < 0 or n % 2 == 0:
        return None
    
    result = "*" * n + "\n";
    spaces = 1;
    n = n - 2
    while n > 0:
        current = " " * spaces + "*" * n + "\n"
        spaces = spaces + 1
        n = n - 2
        result = current + result + current
    
    return result