If the elevator stops at the X floor and Y people go upstairs directly, if they are not satisfied, they will be divided into T, then

t = 3[ 1+2+3]...+(33-x)]+( 1+2+3...+y)+[ 1+2+...+(x-y-2)]

Finishing and preparing to obtain t = m * a 2+n * b 2+R

T is minimum when m * a 2+n * b 2 = 0.

The final solution should be on the 27th floor! !

This method is relatively easy to understand at present, and it has been written in the competition book of senior two! !

Can communicate ~ ~