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 Rust (1.15.1) (judge verdict: Time Limit Exceeded)

use std::io;

fn main() {
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).unwrap();
    let n: usize = buf.trim().parse().unwrap();
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).unwrap();
    let mut min = <i64>::max_value();
    let mut max = <i64>::min_value();
    let a: Vec<i64> = buf.trim().split_whitespace().enumerate().map(|(i, s)| {
        let t = s.parse::<i64>().unwrap() - (i as i64) - 1;
        if t < min {
            min = t;
        }
        if t > max {
            max = t;
        }
        t
    }).collect();
    let mut ans = <i64>::max_value();
    for i in min..max + 1 {
        let t: i64 = a.iter().map(|x| (x - i).abs()).sum();
        if t < ans {
            ans = t;
        }
    }
    println!("{}", ans);
}