How to connect two routers using one LAN cable?

Question

Computer networks

Hello!
Please advise how to solve the problem correctly.
There is one small building connected to the Internet. There are two organizations in the building that want to connect to the Internet. As a matter of fact, the task is to separate the Internet from one LAN cable to two routers in different rooms. As far as I understand, if you use a switch, it will conflict, is there only one IP address? or I'm wrong?

Answer 1

Put an intermediate router at the entrance and separate from it to the other two.