I want to block an entire class A address set and then allow a few of
the addresses within that set to have access.
I figured I could block all the addresses in the set then allow the
specific address(es) that I want.
Like this:

iptables -A INPUT -s nnn.0.0.0/8 -j LOG --log-prefix "IPTABLES DROPPED"
iptables -A INPUT -s nnn.0.0.0/8 -j DROP
iptables -A INPUT -s nnn.0.6.135 -j ACCEPT

But

It is not working and I can't figure out how to do what I want.