Batch, 39 bytes

@ECHO|SET/aa-=%1 2>MER@ @REM>2 1%.OHCE@ 

Reversed

@ECHO.%1 2>MER@ @REM>2 1%=-aa/TES|OHCE@ 

Batch, 34 bytes

@ECHO.%1 2>MER@ @REM>2 1%=-aa/TES@ 

Echoes (ECHO.) the input (%1). The rest of the first line technically redirects STDERR to a file called MER@, but this isn't impactful.
Second line is commented out (REM...).

Reversed

@SET/aa-=%1 2>MER@ @REM>2 1%.OHCE@ 

Uses the arithmetic mode of the set command (SET /a) to subtract (-=) the input (%1) from an undefined variable (a) which is equivalent to 0 - input. Again, the rest of the first line technically redirects STDERR to a file called MER@, but this isn't impactful.
Second line is commented out (REM...).