The Fair Nut lives in n story house. a_i people live on the i-th floor of the house. Every person uses elevator twice a day: to get from the floor where he/she lives to the ground (first) floor and to get from the first floor to the floor where he/she lives, when he/she comes back home in the evening. 

It was decided that elevator, when it is not used, will stay on the x-th floor, but x hasn't been chosen yet. When a person needs to get from floor a to floor b, elevator follows the simple algorithm: 

  * Moves from the x-th floor (initially it stays on the x-th floor) to the a-th and takes the passenger. 
  * Moves from the a-th floor to the b-th floor and lets out the passenger (if a equals b, elevator just opens and closes the doors, but still comes to the floor from the x-th floor). 
  * Moves from the b-th floor back to the x-th. 

The elevator never transposes more than one person and always goes back to the floor x before transposing a next passenger. The elevator spends one unit of electricity to move between neighboring floors. So moving from the a-th floor to the b-th floor requires |a - b| units of electricity.

Your task is to help Nut to find the minimum number of electricity units, that it would be enough for one day, by choosing an optimal the x-th floor. Don't forget than elevator initially stays on the x-th floor. 

Input

The first line contains one integer n (1 ≤ n ≤ 100) — the number of floors.

The second line contains n integers a_1, a_2, …, a_n (0 ≤ a_i ≤ 100) — the number of people on each floor.

Output

In a single line, print the answer to the problem — the minimum number of electricity units.

Examples

Input

3
0 2 1


Output

16

Input

2
1 1


Output

4

Note

In the first example, the answer can be achieved by choosing the second floor as the x-th floor. Each person from the second floor (there are two of them) would spend 4 units of electricity per day (2 to get down and 2 to get up), and one person from the third would spend 8 units of electricity per day (4 to get down and 4 to get up). 4 ⋅ 2 + 8 ⋅ 1 = 16.

In the second example, the answer can be achieved by choosing the first floor as the x-th floor.
import java.util.*;
import java.io.*;
public class Main
{
	static class FastReader 
	{ 
	    BufferedReader br; 
	    StringTokenizer st; 

	    public FastReader() 
	    { 
	        br = new BufferedReader(new
	                 InputStreamReader(System.in)); 
	    } 
	    String next() 
	    { 
	        while (st == null || !st.hasMoreElements()) 
	        { 
	            try
	            { 
	                st = new StringTokenizer(br.readLine()); 
	            } 
	            catch (IOException  e) 
	            { 
	                e.printStackTrace(); 
	            } 
	        } 
	        return st.nextToken(); 
	    }
	    int nextInt() 
	    { 
	        return Integer.parseInt(next()); 
	    } 
	}

	public static void main(String args[])
	{
		FastReader s=new FastReader();
		int n=s.nextInt();
		
		ArrayList<Integer> al=new ArrayList<Integer>();
		while(n-->0)
			al.add(s.nextInt());
		n=al.size();
		if(n==1)
		{
			System.out.println("0");
			System.exit(0);
		}
		int min=1<<30;
		for(int x=1;x<=n;x++)
		{
			int temp=0;
			
			for(int a=2;a<=n;a++)
				temp+=(Math.abs(x-a)+Math.abs(a-1)+Math.abs(x-1))*al.get(a-1)*2;
			if(min>temp)
				min=temp;
		}
		System.out.println(min);
	}
	
}