nano /etc/apt/sources.list
Comment Everthing…
Add These lines
deb http://archive.debian.org/debian wheezy main contrib non-free
deb-src http://archive.debian.org/debian/ wheezy main non-free contrib
deb http://archive.debian.org/debian-security/ wheezy/updates main non-free contrib
deb-src http://archive.debian.org/debian-security/ wheezy/updates main non-free contrib
Note: we use wheezy as an example
apt-get -o Acquire::Check-Valid-Until=false update
apt-get install bc