Ziggyny's World TourDiscrete Mathematics Level 2
The magician, The Great Ziggyny, is planning his next world tour. He knows a total of 7 different illusions but he only has time to perform 4 of them at any show. The Great Ziggyny does not want any two of his shows to be identical, so they cannot contain the same 4 illusions in the same order. What is the most number of cities The Great Ziggyny can perform in during his tour?