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 bisect import bisect


def main():
    n = int(input())
    an = [(i, int(s)) for i, s in enumerate(input().split())][:n]

    ans = sum(a * (-n + 1 + 2 * i) for i, a in an)

    group = {}
    for i, a in an:
        if a not in group:
            group[a] = []
        group[a].append(i)
    group = list(sorted(group.items(), key=lambda t: t[0]))
    # print(group)

    for i in range(len(group) - 1):
        if group[i][0] + 1 == group[i + 1][0]:
            idx_s1 = group[i][1]
            idx_s2 = group[i + 1][1]
            for idx in idx_s1:
                smaller = bisect(idx_s2, idx)
                larger = len(idx_s2) - smaller
                ans = ans - larger + smaller

    print(ans)


if __name__ == '__main__':
    main()
