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. 
N = 2 * 10**5 + 3
n = int(input())
A, cnt = list(map(int,input().split(' '))), {}

s, a = 0, 0

for i in range(n-1,-1,-1):
    a += s
    if (A[i]-1) in cnt:
        a += cnt[A[i]-1]
    if (A[i]+1) in cnt:
        a -= cnt[A[i]+1]
    a -= (n-(i+1))*A[i]
    s += A[i]
    if A[i] not in cnt:
        cnt[A[i]]=0
    cnt[A[i]] += 1

print(a)
