unclean shutdown, checking drives

When I start up, my Ubuntu gives at the splash screen
unclean shutdown, checking drives
and then
/dev/sda5: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.
        (i.e. without -a or -p options)
fsck died with exit status 4
Checking drive /dev/sda5: 94% (stage 4/5, 1087/1097) [fail]

* An automatic file system check (fsck) of the root filesystem failed.
A manual fsck must be performed, then the system restarted.
The fsck should be performed in maintenance mode with the root filesystem in read-only mode.
* The root filesystem is currently mounted in read-only mode.
A maintenance shell will now be started.
After performing system maintenance,press CONTROL-D to terminate
 the maintenance shell and restart the system.
bash: no job control in this shell

WHAT SHOULD I DO? PLEASE HELP!