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. 
from collections import Counter

n = int(input())
arr = [int(i) for i in input().split()]
cnt = Counter()
for i in arr:
    cnt[i] += 1
cur = Counter()
s = sum(arr)
d = 0
i = 0
for val in arr:
    n1 = cnt[val - 1] - cur[val - 1]
    n2 = cnt[val + 1] - cur[val + 1]
    n3 = cnt[val] - cur[val]
    d += s - (n - i) * val
    d -= n1 * (val - 1)
    d += n1 * val
    d -= n2 * (val + 1)
    d += n2 * val
    d -= n3 * val
    d += n3 * val
    i += 1
    s -= val
    cur[val] += 1
print(d)
