[lammps-users] Variable command

Dear all,

I want to use the variable command. But it seems the command doesn't work
correctly. Here's the subscript:

variable L equal 500
variable Ldiv2 equal L/2 \. region 1 block \-{L}-${Ldiv2} INF INF INF INF INF
The calculated value in third line is not -750.
Would you please tell me how to solve this problem?
Any help would be appreciated.

Ali Rajabpour