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())
v = [0] + [int(x) for x in input().split(' ')]
ma = {}
st = 0
ris = 0

for p in range(n,0,-1):
    val = v[p]
    v2 = val+1
    c2 = ma.get(v2, 0)
    v1 = val
    c1 = ma.get(v1, 0)
    v0 = val-1
    c0 = ma.get(v0, 0)
    cnt = n - p - c2 - c1 - c0
    sp = st - v2 * c2 - v1 * c1 - v0 * c0

    ris -= cnt * val
    ris += sp
    st += val
    ma[val] = ma.get(val, 0) + 1
        
print(ris)
