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.*;
import java.math.*;
public class loser
{
    static class InputReader {
        public BufferedReader br;
        public StringTokenizer token;
        public InputReader(InputStream stream)
        {
            br=new BufferedReader(new InputStreamReader(stream),32768);
            token=null;
        }

        public String next()
        {
            while(token==null || !token.hasMoreTokens())
            {
                try
                {
                    token=new StringTokenizer(br.readLine());
                }
                catch(IOException e)
                {
                    throw new RuntimeException(e);
                }
            }
            return token.nextToken();
        }

        public int nextInt()
        {
            return Integer.parseInt(next());
        }

        public long nextLong()
        {
            return Long.parseLong(next());
        }
    }
    static class card{
        long a;
        int i;
        public card(long a,int i)
        {
            this.a=a;
            this.i=i;
        }
    }
    static class sort implements Comparator<pair>
    {
        public int compare(pair o1,pair o2)
        {
            if(o1.a!=o2.a)
                return (int)(o1.a-o2.a)*-1;
            else
                return (int)(o1.b-o2.b)*-1;
        }
    }
    static class sort1 implements Comparator<pair>
    {
        public int compare(pair o1,pair o2)
        {
            if(o1.a!=o2.a)
                return (int)(o1.a-o2.a);
            else
                return (o1.b-o2.b)*-1;
        }
    }
    static class extra{
        static void shuffle(int a[])
        {
            List<Integer> l=new ArrayList<>();
            for(int i=0;i<a.length;i++)
                l.add(a[i]);
            Collections.shuffle(l);
            for(int i=0;i<a.length;i++)
                a[i]=l.get(i);
        }

        static long gcd(long a,long b)
        {
            if(b==0)
                return a;
            else
                return gcd(b,a%b);
        }

        static boolean valid(int i,int j,int r,int c)
        {
            if(i>=0 && i<r && j>=0 && j<c)
                return true;
            else
                return false;
        }
    }
    static class pair{
        int a;int b;
        public pair(int a,int b)
        {
            this.a=a;
            this.b=b;
        }
    }
    static InputReader sc=new InputReader(System.in);
    static PrintWriter out=new PrintWriter(System.out);
    public  static void main(String[] args) 
    {
        solver s=new solver();
        int t=1;
        while(t>0)
        {
            s.solve();
            t--;
        }
    }
    static class solver
    {
        void solve()
        {
           int n=sc.nextInt();
           pair c[]=new pair[n];
           int t[]=new int[n];
           for(int i=0;i<n;i++)
           {
                t[i]=sc.nextInt();
               c[i]=new pair(t[i],i+1);
           }
           Arrays.sort(c,new sort1());
           long sum=0;
           int x=c[n-1].b;
           for(int i=1;i<=n;i++)
           {
               if(i<=x)
               {
                   sum+=t[i-1]*4*(x-1);
               }
               else
               sum+=t[i-1]*4*(i-1);
           }
           System.out.println(sum);
        }
    }
}
