IPTables - Block Internet Access To SSH (22) Except Verified IP's

I recently looked at my secure and mesaages log and have been getting a lot of failed SSH root login attempts. So I thought I better do something about it.

Ideally I want to allow SSH login from just 3 remote public IP's, and block all others from even trying

How would you go about implementing this?

I have tried using IPTables, but I think im getting the rule wrong somewhere.

Here is what I have:

Code:
## Access to SSH from Pre-approved IP Addresses ONLY ##

iptables -I INPUT 1 -p tcp --dport 22 -s 123.123.123.123 -j ACCEPT
iptables -I INPUT 2 -p tcp --dport 22 -s 123.123.123.124 -j ACCEPT
iptables -I INPUT 3 -p tcp --dport 22 -s 123.123.123.125 -j ACCEPT
iptables -I INPUT 4 -p tcp --dport 22 -s 0.0.0.0 -j DROP

However this still lets me login from IPs not in the list above?