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

ps = a[0]
ans = 0
h = {a[0]:1}
hv = {a[0]: a[0]}
def gv(h, k):
    if k in h:
        return h[k]
    else:
        return 0

for i in range(1, n):
    c = i - gv(h,a[i]) - gv(h,a[i]-1) - gv(h,a[i]+1)
    cps = ps - gv(hv,a[i]) -gv(hv,a[i]-1)-gv(hv,a[i]+1)
    ans += a[i]*c - cps
    #print(a[i], c, cps)
    #print(ans)
    if a[i] not in h:
        h[a[i]] = 0
        hv[a[i]] = 0
    h[a[i]] += 1
    hv[a[i]] += a[i]
    ps += a[i]
print(ans)