VPN IPSec tunnel for two ISP on two ISP

Hello.
I can`t find example configuration for vpn ipsec tunnel (isp 2x2).
We have Office 1 with (ISP 1 and ISP 2) and Office 2 with (ISP 1 and ISP 2). Need connect this office with fail over vpn ipsec tunnel.
How i can do this?
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