Instructions
Replace your /etc/apt/sources.list contents to one of these sections
[Debian 12]
deb http://repo.iut.ac.ir/debian/ bookworm main
deb http://repo.iut.ac.ir/debian/ bookworm-updates main
[Debian 11]
deb http://repo.iut.ac.ir/debian/ bullseye main
deb http://repo.iut.ac.ir/debian/ bullseye-updates main
[Debian 10]
deb http://repo.iut.ac.ir/debian/ buster main
deb http://repo.iut.ac.ir/debian/ buster-updates main
[Debian 9]
deb http://repo.iut.ac.ir/debian/ stretch main
deb http://repo.iut.ac.ir/debian/ stretch-updates main