Problem:
Score : 300 points

Problem Statement

Snuke has an integer sequence A of length N.

He will freely choose an integer b.
Here, he will get sad if A_i and b+i are far from each other.
More specifically, the sadness of Snuke is calculated as follows:

abs(A_1 - (b+1)) + abs(A_2 - (b+2)) + ... + abs(A_N - (b+N))

Here, abs(x) is a function that returns the absolute value of x.

Find the minimum possible sadness of Snuke.

Constraints

1 \leq N \leq 2 \times 10^5

1 \leq A_i \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 A_2 ... A_N

Output

Print the minimum possible sadness of Snuke.

Sample Input 1

5
2 2 3 5 5

Sample Output 1

2

If we choose b=0, the sadness of Snuke would be abs(2-(0+1))+abs(2-(0+2))+abs(3-(0+3))+abs(5-(0+4))+abs(5-(0+5))=2.
Any choice of b does not make the sadness of Snuke less than 2, so the answer is 2.

Sample Input 2

9
1 2 3 4 5 6 7 8 9

Sample Output 2

0

Sample Input 3

6
6 5 4 3 2 1

Sample Output 3

18

Sample Input 4

7
1 1 1 1 2 3 4

Sample Output 4

6

Solution in JavaScript (node.js v5.12) (judge verdict: Runtime Error)

const sum = arr => arr.reduce((prev, current) => { return prev + current; }, 0);

function Main (input) {
  const inputs = input.split(/\s/g).filter((num) => num).map(num => parseInt(num)).slice(1);
  const max = Math.max(...inputs);
  const results = new Array(max + 1).fill('').map((value, selected) => {
    const plus = sum(inputs.map((num, index) => Math.abs(num - (selected + (index + 1)))));
    const minus = sum(inputs.map((num, index) => Math.abs(num - ((-1 * selected) + (index + 1)))));
    return Math.min(plus, minus);
  });
  console.log('%s', Math.min(...results));
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));