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. 
def main():
    n = int(input())
    v = list(map(int, input().split()))
    m = dict()
    res = 0

    for i in v:
        if i not in m:
            m[i] = 0
        m[i] += 1
    k = v.copy()

    for i in range(n - 1, 0, -1):
        k[i - 1] = k[i] + k[i - 1]

    for i in range(0, n - 1):
        res += -(n - i - 1) * v[i] + k[i + 1]
        m[v[i]] -= 1
        if v[i] + 1 in m:
            res -= m[v[i] + 1]
        if v[i] - 1 in m:
            res += m[v[i] - 1]

    print(res)


if __name__ == '__main__':
    main()
