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. 
import sys
def main():


 N = int(input())
 A = list(map(int, input().split()))

 cnt = dict()
 pref = 0
 ans = 0
 for i in range(N):
    v = A[i]
    cnt[v-1] = cnt.get(v-1, 0)
    cnt[v] = cnt.get(v, 0)
    cnt[v+1] = cnt.get(v+1, 0)
    add = pref- (v-1) * cnt[v-1] - v * cnt[v] - (v+1)*cnt[v+1]
    num_pairs = i - cnt[v-1] - cnt[v] - cnt[v+1]
    add -= v * num_pairs
    ans -= add
    pref += v
    cnt[v] += 1
 print(ans)


main()
