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. 
maxn = 200005
a = [0 for i in range(maxn)]
sum = [0 for i in range(maxn)]
mp = {}

n = int(input())

input = raw_input().split()
for i in range(n):
    a[i] = int(input[i])
    if not mp.__contains__(a[i]):
        mp[a[i]] = 0
    mp[a[i]] += 1

ans = 0

i = n - 1
while i >= 0:
    sum[i] = a[i] + sum[i + 1]
    i -= 1

for i in range(n - 1):
    mp[a[i]] -= 1
    if mp[a[i]] == 0:
        mp.__delitem__(a[i])
    tmp = sum[i + 1] - a[i] * (n - i - 1)
    if mp.__contains__(a[i] + 1):
        tmp -= mp[a[i] + 1]
    if mp.__contains__(a[i] - 1):
        tmp += mp[a[i] - 1]
    ans += tmp

print ans