Router in bridge mode

I have a cisco 2621 router left in town A, settings as below. I have a cisco
2621 router
right in town B, settins as below. I cannot change the ip addresses or
interfaces.
To connect them I thought I could use a cisco 2621 router in bridge mode and
made a
config 'middle' as below. It doesn't work. What is a good solution for this
problem? Help.

Router left:
int f0/0
description connected to bridge in the middle via x-cable
ip addr 10.10.10.2 255.255.255.0
no shut
int f0/1
description connected to P network
ip addr 172.16.20.1 255.255.255.0
no shut

Router middle:
int f0/0
description connected to router left via x-cable
bridge-group 1
no shut
int s0/0
description connected to router right via serial cable
bridge-group 1
no shut

Router right:
int f0/0
description connected to ICC network
ip addr 172.16.10.1 255.255.255.0
no shut
int s0/0
description connected to router middle via serial cable
ip addr 10.10.10.1 255.255.255.252
clo rat 64000
no shut