Let's denote a function 

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You are given an array a consisting of n integers. You have to calculate the sum of d(ai, aj) over all pairs (i, j) such that 1 ≤ i ≤ j ≤ n.

Input

The first line contains one integer n (1 ≤ n ≤ 200000) — the number of elements in a.

The second line contains n integers a1, a2, ..., an (1 ≤ ai ≤ 109) — elements of the array. 

Output

Print one integer — the sum of d(ai, aj) over all pairs (i, j) such that 1 ≤ i ≤ j ≤ n.

Examples

Input

5
1 2 3 1 3


Output

4


Input

4
6 6 5 5


Output

0


Input

4
6 6 4 4


Output

-8

Note

In the first example:

  1. d(a1, a2) = 0; 
  2. d(a1, a3) = 2; 
  3. d(a1, a4) = 0; 
  4. d(a1, a5) = 2; 
  5. d(a2, a3) = 0; 
  6. d(a2, a4) = 0; 
  7. d(a2, a5) = 0; 
  8. d(a3, a4) = - 2; 
  9. d(a3, a5) = 0; 
  10. d(a4, a5) = 2. 
import java.math.BigInteger;
import java.util.*;
final public class main{
    static Map<Integer,Integer> M=new TreeMap<Integer, Integer>();
    static int safeget(int x)
    {
        Integer i=M.get(x);
        if(i==null) return 0;
        else
        {
            //System.out.println("OI"+i.intValue());
            return i.intValue();
        }
    }
    static public void  main(String argv[])
    {
        int N;
        Scanner sc=new Scanner(System.in);
        N=sc.nextInt();
        int i;
        BigInteger ans=BigInteger.ZERO;

        for(i=0;i<N;i++)
        {
            int x=sc.nextInt();
            long val=i*2+1-N-safeget(x-1)-safeget(x+1);
            BigInteger b1=BigInteger.valueOf(val);
            BigInteger b2=BigInteger.valueOf(x);
            ans=ans.add(b1.multiply(b2));

            BigInteger c1=BigInteger.valueOf(safeget(x-1));
            BigInteger c2=BigInteger.valueOf(x-1);

            BigInteger d1=BigInteger.valueOf(safeget(x+1));
            BigInteger d2=BigInteger.valueOf(x+1);
            ans=ans.add(c1.multiply(c2));
            ans=ans.add(d1.multiply(d2));


            int t=safeget(x);
            //System.out.println(t+1);
            M.put(x,t+1);
            //

        }
        System.out.print(ans);


    }
}