Great problem. May my critisism inspire you to write many more problems, Igor"I think problem descriptions should withstand the

reality check, otherwise they are misleading."

little joey

Why are you considering retirement, BTW? Please don't...

OK, one minor point of critique. In your discussion of the first sample you write:

But the second elevator takes 5 seconds per floor, so it takes 85 seconds to go from floor 30 to floor 13, and 85 seconds to go back again. The numbers then add up to 1295.In the first example, the worst case is when elevator 1 is on floor 99 and will take 990 seconds to reach floor 0. You will then take it to floor 13 in 130 seconds, spend 5 second exiting and calling elevator 2, which is on floor 30. It will take 170 seconds to reach you and 170 seconds to take you to floor 30. The total is 1295 seconds.