P6490 [COCI 2010/2011 #6] RAZINE

Given a sequence of length $n$, you may subtract a number from some elements so that the whole sequence becomes **strictly increasing**. You need to find the minimum possible value of the sum of all numbers subtracted. For example, for a sequence of length $3$: $5,5,5$. The best plan is $5-2,5-1,5$, i.e. $3,4,5$. Then the sum of all subtracted numbers is $2+1=3$, which is the minimum.

The first line contains an integer $n$, representing the length of the sequence. The second line contains $n$ integers describing the sequence.

Output one integer in one line, representing the minimum total sum.

#### Constraints and Notes For $100\%$ of the testdata, it is guaranteed that $1\le n\le 100$, and all numbers in the sequence are positive integers not greater than $20000$. #### Notes **Translated from [COCI2010-2011](https://hsin.hr/coci/archive/2010_2011/) [CONTEST #6](https://hsin.hr/coci/archive/2010_2011/contest6_tasks.pdf) *T3 RAZINE***。 Translated by ChatGPT 5