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. 
dic = {}
n = int(input())
arr = [int(x) for x in input().split()]
for x in arr:
    if x not in dic:
        dic[x] = 1
    else:
        dic[x] += 1
total = 0
su = 0
for x in arr:
    su += x
for x in range(len(arr)):
    su -= arr[x]
    hold = 0
    cnt = n-x-1
    for y in range(-1,2):
        num = arr[x]+y
        if num in dic:
            hold += dic[num]*(num)
            cnt -= dic[num]
    dic[arr[x]] -= 1
    hold -= arr[x]
    cnt += 1
    su -= hold
    total += (su-(arr[x]*cnt))
    su += hold
print(total)
