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. 
tmp = input();
ans = 0
arr = [int(x) for x in input().split(' ')]
n = len(arr)
m = {}
sum = 0

for i in range(0, n):
  m[arr[i]] = m.get(arr[i], 0) + 1 
  sum += arr[i]

for i in range(0, n):
  m[arr[i]] = m.get(arr[i], 0) - 1
  sum -= arr[i]
  c1 = m.get(arr[i] - 1, 0)
  c2 = m.get(arr[i], 0)
  c3 = m.get(arr[i] + 1, 0)
  cur_sum = sum - (c1 * (arr[i] - 1) + c2 * arr[i] + c3 * (arr[i] + 1))
  cur_cnt = n - i - 1 - c1 - c2 - c3
  ans += cur_sum - cur_cnt * arr[i]

print(ans)
