Fortigate 30E. Dual WAN port

Hello,

I'm configuring Fortigate 30E. I configured one public IP on WAN port for internet connection. I need now two wan port because i need to install a web server I have only one WAN port that i'm using for internet connection I have a range of public IP from my ISP 198.116.74.64/29 I configured 198.116.74.65 in WAN1. This WAN1 allow internet connection for my devices (hosts and pcs) I need to install a web server.

I set up LAN2 as wan port but when i insert 198.116.74.66 it says there's a conflict with wan1 port How can i solve?

thanks