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 collections import defaultdict

N = int(input())
A = list(map(int, input().split(' ')))
S1 = defaultdict(int)
S2 = defaultdict(int)
for i in range(1, N): 
    S2[A[i]] += 1
res = 0

for i in range(N):
    res += i * A[i]
    res -= (N-i-1) * A[i]
    res -= (S1[A[i]-1] + S1[A[i]] + S1[A[i]+1]) * A[i]
    res += (S2[A[i]-1] + S2[A[i]] + S2[A[i]+1]) * A[i]
    S1[A[i]] += 1
    if i < N-1:
        S2[A[i+1]] -= 1

print(res)
