Rapid detection technology can detect communication failures with adjacent devices as early as possible so that the system can take timely measures to ensure uninterrupted business.

The four routers R1, R2, R3 and R4 enable OSPF to establish neighbor relationships. The topology and related parameters are shown in the figure.

At this time, R2 is disconnected for some reason, so the Hello report transmitted between R1, R3 and R4 In the text, which of the following is the value of the BDR field?