conditional formating with multiple entries
 

i am currently working on setting up a tracker for people being gone. i want
the cells to change yellow if the person is gone for 4 or less days and to
turn blue if they are gone for 5 or more days.

the cells in the spreadsheet already make an "f" for the first day an "l"
for the last day and "X" for any day in between. the auto changing cells
work perfect and work with another sheet. the fomula look like...

=IF(INPUT!$D2=Tracker!D$2,"F",IF(INPUT!$E2=Tracker !D$2,"L",IF(Tracker!C3="X","X",IF(Tracker!C3="F"," X",""))))

do you have any suggestions to maybe this formula to be more easily
understood be other commands or is it a user error?
p.s. this formula is pretty much just repeated from A1:A300 and to IL1:IL300.