One mathematical teacher was giving lessons in combination theories to various
students. It so happened that one day he had two students from another town,
and as their lesson took longer than they thought it would, they got late for
their train and the professor offered them to lodge at his place for the
night. They arranged it so: the professor and his wife were in one room, the
second room was occupied by their daughter, and both the students were in the
third room.
One of the students woke up in the middle of the night and thought: 'Why the
hell am I sleeping here with this guy, when I could go and visit the
professor's daughter in her room.' He opened the first door, saw two people in
bed, understood that it was the professor, so he opened the second room and
went there. A bit later, the professor awoke and had a thought that since
there were those two students and his daughter was all alone, maybe he should
go and sleep with her to prevent anything from happening. He opened one room,
saw two people, thought these were two students, opened the other and went in
there. Now, a little later the other student woke up. As you have probably
guessed, he went in the footsteps of his friend, in search of the daughter.
Opened the first door, saw two heads on the pillow, thought it to be the
professor and his wife, and went inside the other room.
It is morning. The professor wakes up. Alone. In the students' room. Hmm...
Looks into one room: student with daughter. Looks into other room: student
with his own wife. Scratches his head and says: Well, I've taught combinations
for many years, but I've never seen such a screwed combination as this!