I was solving this question: http://mirror.codeforces.com/contest/479/problem/B

The output specification states that: "Note that in the process of performing operations the heights of some towers can become equal to zero."

Consider the second test case:

3 4

2 2 4

We can arrive at a better solution than the one given by doing the following operations:

1 2

1 2

Now the towers are: 4 4 with instability 0 (as tower 1 no longer exists). But the answer states minimum as 1.

Can somebody please help me understand what I am misunderstanding here?

EDIT: So I understood that I should not have assumed that a tower with no blocks will not exist. I am now interested in this variant:

Suppose a tower with no blocks ceases to exist. How would one solve this problem now? I tried but could not come on with a working solution. Example: There are 3 towers initially: 2 5 7. Suppose we can only move two blocks. Then we can achieve zero instability. Any help is appreciated.