The classless inter-domain routing notation (CIDR) allows IP address ranges to be specified. For example, the address 123.145.167.189/32 refers to that exact IP address whereas 123.145.167.189/31 refers to the IP addresses 123.145.167.189 and 123.145.167.190. The number of addresses is calculated as $$2^{32-n}$$ where $$n$$ in the above two examples is 32 and 31 respectively. That is, 1 ($$2^0$$) and 2 ($$2^1$$).