This is not a Hack guys just a trick enjoy.

The command processor CMD.EXE comes with a mini-calculator that can perform simple arithmetic on 32-bit signed integers:

C:\>set /a 2+2
4
C:\>set /a 2*(9/2)
8
C:\>set /a (2*9)/2
9
C:\>set /a "31>>2"
7

Note that we had to quote the shift operator since it would otherwise be misinterpreted as a "redirect stdout and append" operator.
For more information, type set /? at the command prompt.