vpn ipsec 3 ip

Hello!
There is a task to build a tunnel between 2 mikrotik, the only problem is that mikrotik A - one wan ip, mikrotik B - two wan ip address

When the two ip adress A and B by 2 ip no problem!

There is a problem when only one tunnel is established depending on the provider looks through a main route on mikrotik B!

Help, me!