How to block non-localhost packets with iptables

All PCs have br0 and br1 interfaces, and all IPs are in the same network 192.168.1.0/24 and 192.168.2.0/24. IP forwarding is enabled in all PCs.

All PCs are connected to the same switch. When no rules defined in the iptables, all PCs can ping and ssh to each other.

PC1:    br0:         192.168.1.1    br1:         192.168.2.1    rules in FORWARD:        iptables -A FORWARD -i br0 -o br1 -j ACCEPT        iptables -A FORWARD -i br1 -o br0 -j ACCEPTPC2:    br0:         192.168.1.2    br1:         192.168.2.2    rules in FORWARD:        iptables -A FORWARD -i br0 -o br1 -j ACCEPT        iptables -A FORWARD -i br1 -o br0 -j ACCEPTPCn:    br0:         192.168.1.n    br1:         192.168.2.n    rules in FORWARD:        iptables -A FORWARD -i br0 -o br1 -j ACCEPT        iptables -A FORWARD -i br1 -o br0 -j ACCEPT

Now, I want to block PC1 from accessing PC2 and PCn, and vice versa (PC2 and PCn can't access PC1), that is, PC1 only allowed to send and receive all packets in localhost.

iptables -A INPUT -j DROPiptables -A OUTPUT -j DROP

Is is enough for blocking all non-localhost packets with the above two iptables rules in the INPUT and OUTPUT? If not, what rules should be used to block all non-localhost packets?