Minimize The Difference

Recently, Kiki are asked to arrange a competition. Before the competition, everyone have an expectation of the ranking. To make all the players happy , Kiki wants to minimize the sum of all the players’ difference. We define the difference of a player as |ai-bi|, ai stands for one’s expected ranking ,and bi stands for one’s final ranking.

There are several test cases.
Each case begins with an integer n ,(n<= 100)stands for the number of players in this competition.
Then follows n lines ,each line contains a string s and an integer m,(the string will contains no more than 20 characters and no space in it, 1<=m<=n) stands for the name of the player and his expected ranking.

The output contains one line for each data set : the minimum sum of differences Kiki can get.

7
a 1
b 2
c 2
d 1
e 5
g 7
f 7

5

Hint
One possible solution
1. a2. d3. b4. c5. e6. g7. f

dandelion

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