903_D. Almost Difference
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. 
```python
from sys import stdin, stdout
n = int(stdin.readline())
a = [int(i) for i in stdin.readline().split()]
d = dict()
ans, sm = 0, 0
for i in range(n):
    if a[i] not in d.keys():
        d[a[i]] = 0
    d[a[i]] += 1
    ans += i * a[i] - sm
    if (a[i] + 1) in d.keys():
        ans += 1 * d[a[i] + 1]
    if (a[i] - 1) in d.keys():
        ans -= 1 * d[a[i] - 1]
    sm += a[i]
stdout.write(str(ans))

```