\(6^{th}\) round, March \(4^{th}\), 2011

Mirko has developed his own video game. The game has N levels and each successfully completed level
is worth a certain number of points, which add up to the player’s total score on an online rank list of all
players. Mirko has ordered his levels by difficulty from the easiest to the most difficult, but he has
made a mistake and made some difficult levels worth less points than some of the easier ones.
To overcome this problem, Mirko has decided to reduce the number of points for certain levels with
the goal of making the point sequence strictly increasing (so in the end easier levels are worth less
points than the difficult ones).
Help Mirko fix his video game in such a way that the total number of points reduced is minimal.
Final points have to be positive. You can assume that a solution exists for each test case.

The first line of input contains a positive integer \(N\) (\(N \le 100\)), the number of words.

The following \(N\) lines contain the list of words found, one word per line. Each word consists of at most \(10\) lowercase letters.

The first and and only line of output should contain one numb\(er - th\)e minimum total number of points
Mirko has to subtract to fulfill requirements given in the task statement above.

riseoj 작성

출처 COCI 2010/2011 Contest 6