Not sure why you want to do that.
nice - run a program with modified scheduling priority
nice [OPTION] [COMMAND [ARG]...]
Run COMMAND with an adjusted niceness, which affects process scheduling. With no COMMAND, print the current niceness.
Nicenesses range from -20 (most favorable scheduling) to 19 (least favorable).
add integer N to the niceness (default 10)
Think you want: