This is the way Christmas is adding up this year.
1+1=2 (Willow and The Professor)
2+1=3 (The Grad Student)
3+2=5 (Kiti and The New Boy)
5-2=3 (Kiti and The New Boy leave)
3+2=5 (Kiti and The New Boy return)
5+2=7 (Chaplain Dan and The Princess)
7-2=5 (Chpl. Dan and The Princess leave)
5+2=7 (MamaMia and The Marine arrive)
7-2=5 (Kiti and The New Boy fly away New Year's Eve)
5-3=2 (MM, The Marine and TGS go home)
Willow and The Professor, empty nest in January.
I should have made up a spread sheet.