Help! My debian sid cannot boot, "A manual fsck must be performed"

[Star Liu <minxinjianxin@gmail.com>]

When I boot my debian sid 5 minutes ago, I got this error message:
-----------------------------------------------------------------------------------------------------------
/dev/sda4: unexpected inconsistency; run fsck manually.(i.e., without
-a or -p options)
fsck died with exit status 4
failed (code 4)
An automatic file system check(fsck) of the root filesystem failed. A
manual fsck must be performed. The fsck should be performed in
maintance mode with the root filesystem mounted in read-only mode.
failed!
---------------------------------------------------------------------------------------------------------------

i have entered the maintance mode, but i don't know how to recover my
filesystem. anyone can help me? thank you. this is the first time i
encounter a serious problem with debian.