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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<iostream>
#include<string>
#include<fstream>
#include<algorithm>
#include<vector>
#include<cstdio>
#include<cmath>

typedef long long int ll;
using namespace std;

int main(void)
{
	ll i, t;
	long long int n;
	double min=1000000000;
	double mina = 100000000;
	double max = 0;
	double sum = 0;
	cin >> n;
	vector<double> a(n);
	for (i = 0; i < n; i++)
	{
		cin >> a[i];
	}
	for (i = 0; i < n; i++)
	{
		if (max < a[i])
		{
			max = a[i];
		}
	}
	for (i = 0; i < n; i++)
	{
		if(mina>a[i])
		{ 
			mina = a[i];
		}
	}
	for (i = -n/2; i <n/2; i++)
	{
		sum = 0;
		for (t = 0; t < n; t++)
		{
			sum += abs(a[t] - (i + t + 1));
		}
		if (min > sum)
		{
			min = sum;
		}
	}

	cout << min << endl;
	return 0;
}