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.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
	// write your code here
        Scanner sc=new Scanner(System.in);
        BigInteger n=sc.nextBigInteger();
        BigInteger[] a=new BigInteger[200001];
        for(BigInteger i=BigInteger.ZERO;i.compareTo(n)<0;i=i.add(BigInteger.ONE))
            a[i.intValue()]=sc.nextBigInteger();
        BigInteger sum=BigInteger.ZERO;
        BigInteger ans=BigInteger.ZERO;
        Map<BigInteger,BigInteger> cnt=new HashMap<>();
        BigInteger temp=BigInteger.ZERO;
        for(BigInteger i=n.subtract(BigInteger.ONE);i.compareTo(BigInteger.ZERO)>=0;i=i.subtract(BigInteger.ONE))
        {
            ans=ans.add(sum.subtract((n.subtract(BigInteger.ONE).subtract(i)).multiply(a[i.intValue()])));
            if(cnt.containsKey(a[i.intValue()].subtract(BigInteger.ONE)))
                ans=ans.add(cnt.get(a[i.intValue()].subtract(BigInteger.ONE)));
            if(cnt.containsKey(a[i.intValue()].add(BigInteger.ONE)))
                ans=ans.subtract(cnt.get(a[i.intValue()].add(BigInteger.ONE)));
            if(cnt.containsKey(a[i.intValue()]))
            {
                temp = cnt.get(a[i.intValue()]).add(BigInteger.ONE);
                cnt.remove(a[i.intValue()]);
            }
            else temp=BigInteger.ONE;
            cnt.put(a[i.intValue()],temp);
            sum=sum.add(a[i.intValue()]);
        }
        System.out.println(ans);
    }
}
