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 BigInt {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt() , x;
        
        long[] cum = new long[200010];
        cum[0] = 0;
        
        BigInteger ans = new BigInteger("0");
        BigInteger tmp,lala;
        
        Map<Integer,Integer> map = new HashMap<Integer,Integer>();
        
        int haha;
        
        for(int i=1;i<=n;i++) {
            x = sc.nextInt();
          
            tmp = new BigInteger(Integer.toString(i-1));
            tmp = tmp.multiply(BigInteger.valueOf(x));
            tmp = tmp.subtract(BigInteger.valueOf(cum[i-1]));
            ans = ans.add(tmp);
            
            if(map.containsKey(x-1)) haha = map.get(x-1);
            else haha = 0;
            ans = ans.subtract(BigInteger.valueOf(haha));
            
            if(map.containsKey(x+1)) haha = map.get(x+1);
            else haha = 0;
            ans = ans.add(BigInteger.valueOf(haha));
            
            if(map.containsKey(x)){
                haha = map.get(x);
                map.put(x, haha+1);
            }
            else{
                map.put(x, 1);
            }
            cum[i] = cum[i-1] + x;
        }
        System.out.println(ans.toString());   
    }    
}
