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 = int(input())
a = [int(i) for i in input().split()]
b = []
c = {}
s = 0
for i in range(n):
  if i == 0:
    b.append(a[i])
  else:
    b.append(b[-1]+a[i])
    try: lower = c[a[i]-1]
    except KeyError: lower = 0
    try: this = c[a[i]]
    except KeyError: this = 0
    try: upper = c[a[i]+1]
    except KeyError: upper = 0
    tokeep = i - lower - this - upper
    s += tokeep*a[i] - b[i-1] + lower*(a[i]-1) + this*a[i] + upper*(a[i]+1)
  try: c[a[i]] += 1
  except KeyError: c[a[i]] = 1
print(s)