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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
int abs(int A,int I,int B)
{
  int x;
  x=A-(B+I);
  if(x<0){
    x=x*(-1);
  }
  return x;
}
int main(void)
{
  int N;
  int a;
  int c=0;
  int d=0;
  int f,min;
  
  scanf("%d",&N);
int abc[N];
    for(int i=0;i<=N-1;i++)
   {
     scanf("%d",&a);
     abc[i]=a;//N
    }
    for(int b=0;b<=N;b++){
      for(int k=0;k<=N-1;k++)
      {
        c=c+abs(abc[k],k,b);
        if(k==(N-1))
        {
          if(b==0)
          {
          min=c;
          }
          if(min>c)
          {
              min=c;
          }
            c=0;
        }
      }
    }
    for(int b=0;b>=N*(-1);b--){
        for(int k=0;k<=N-1;k++)
        {
          d=d+abs(abc[k],k,b);
          if(k==(N-1))
          {
            if(b==0)
            {
            min=d;
            }
            if(min>d)
            {
                min=d;
            }
            d=0;
          }
        }
      }
     printf("%d",min);
}