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. 
//package EducationalCodeForcesRound34;

import java.math.BigInteger;
import java.util.HashMap;
import java.util.Scanner;

/**
 * Created by Pranav ps on 12-12-2017.
 */
public class D {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long[] arr = new long[n];
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextLong();
        }
        BigInteger prefixSum = BigInteger.ZERO;
        BigInteger ans = BigInteger.ZERO;
        HashMap<BigInteger,Integer> hm = new HashMap<>();
        for (int i = 0; i < n; i++) {
            BigInteger local = BigInteger.ZERO;
            BigInteger temp = BigInteger.valueOf(arr[i]);
            local = local.add(BigInteger.valueOf(i).multiply(temp));
            local = local.subtract(prefixSum);
            BigInteger a = temp.subtract(BigInteger.ONE);
            int oneLess = (hm.containsKey(a))?hm.get(a):0;
            BigInteger b = temp.add(BigInteger.ONE);
            int oneMore = (hm.containsKey(b))?(hm.get(b)):0;

            int equal = (hm.containsKey(temp))?(hm.get(temp)):0;

            local = local.add(a.multiply(BigInteger.valueOf(oneLess)));
            local = local.add(b.multiply(BigInteger.valueOf(oneMore)));
            local = local.add(temp.multiply(BigInteger.valueOf(equal)));

            local = local.subtract(temp.multiply(BigInteger.valueOf(equal+oneLess+oneMore)));
            ans = ans.add(local);
            prefixSum = prefixSum.add(temp);
            if(!hm.containsKey(temp))
                hm.put(temp,0);
            hm.put(temp,hm.get(temp)+1);
        }
        System.out.println(ans);
    }
}
