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 = [int(i) for i in input().split()]
map = {nums[0]: 1}
result = 0
partial = nums[0]
for a in range(1, n):
    if nums[a] in map.keys():
        map[nums[a]] += 1
    else:
        map.update({nums[a]: 1})
    result += a * nums[a] - partial
    partial += nums[a]
    new = 0
    if nums[a] - 1 in map.keys():
        new -= map[nums[a] - 1]
    if nums[a] + 1 in map.keys():
        new += map[nums[a] + 1]
    result += new

print(result)