ssh to a remote server via gateway server

[L]

Hi,
I routinely login a remote server via a 'gateway' machine. For example, I
need to login to PC B using ssh. But this PC B is behind a firewall.ssh port
on PC A is open.

As a result, I have to login  PC A via ssh, then ssh PC B from PC A.

Is there ssh command line option that I can directly ssh to PC B?

Thanks
Y