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. 
if __name__ == '__main__':
    n = int(input().strip())
    arr = [int(i) for i in input().strip().split(" ")]
    dic = {arr[0]: 1}
    ic = [0 for i in range(n)]
    isu = [0 for i in range(n)]
    pre = [arr[0]]
    for i in range(1, n):
        pre.append(pre[i - 1] + arr[i])
    for i in range(1, n):
        ici, isi = 0, 0
        if arr[i] in dic:
            ici += dic[arr[i]]
            isi += arr[i] * dic[arr[i]]
        if arr[i] - 1 in dic:
            ici += dic[arr[i] - 1]
            isi += (arr[i] - 1) * dic[arr[i] - 1]
        if arr[i] + 1 in dic:
            ici += dic[arr[i] + 1]
            isi += (arr[i] + 1) * dic[arr[i] + 1]
        ic[i], isu[i] = ici, isi
        if arr[i] in dic:
            dic[arr[i]] += 1
        else:
            dic[arr[i]] = 1
    ans = 0
    for i in range(1, n):
        ans += (arr[i] * i) - pre[i - 1] - ic[i] * arr[i] + isu[i]
    print(ans)
