you have two towers
tower one has "x" numbers of levels
tower two has "y" numbers of levels
there can only be one man in each tower
you cannot put the men in the same level
how many configurations can you make, not knowing which tower has more levels
this could be homework, who knows, don't kill this because of that, it's just an interesting problem
In the end you have "n" number of towers each with an unknown number of levels
there can only be one man in each tower
you cannot put men in the same level
and again how many configurations can you make, without organizing the towers by the number of levels