Custom Column for Shift

I have a column with the hour of the day noted, and need to figure out shift based on it. 

For example: 

Between Hour 6 and Hour 18 its supposed to be 'First Shift' and

Between Hour 18 and Hour 6 its supposed to be 'Third Shift'

I tried using this custom formula:

If [Hour] >= 6 and [Hour] < 18 then "First" else "Third"

But this gives me a 'Token Eof expected' error:

Any ideas why this is happening?

Appreciate the help!

Thanks!

G