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. 
n = int(input())
nums = list(map(int, input().split()))
pref_sums = []
helper = []
all_numbers = {i: 0 for i in nums}
for i in nums:
    all_numbers[i] += 1
cur = {}
for i in range(n):
    c = nums[i]
    if c not in cur.keys():
        cur[c] = 1
    else:
        cur[c] += 1
    lesser_all = 0
    lesser_cur = 0
    bigger_all = 0
    bigger_cur = 0
    if c - 1 in all_numbers.keys():
        lesser_all = all_numbers[c - 1]
    if c - 1 in cur.keys():
        lesser_cur = cur[c - 1]
    if c + 1 in all_numbers.keys():
        bigger_all = all_numbers[c + 1]
    if c + 1 in cur.keys():
        bigger_cur = cur[c + 1]
    helper.append((lesser_all - lesser_cur, bigger_all - bigger_cur))
    if len(pref_sums) == 0:
        pref_sums.append(c)
    else:
        pref_sums.append(c + pref_sums[-1])
answer = 0
for i in range(n):
    k = helper[i][1]
    l = helper[i][0]
    mul = n - i - 1
    s = pref_sums[n - 1] - pref_sums[i]
    answer += s - mul * nums[i] - k + l
print(answer)
