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 = map(int, raw_input().strip().split(' '))
p = dict()
c = dict()
jsum = 0
substract_left = 0
for e in xrange(n):
    p[e] = (e*a[e] - a[e]*(n-e-1))
    if c.get(a[e],None) == None:
        c[a[e]] = 0

    if c.get(a[e]-1,None) != None:
        substract_left = substract_left + c[a[e]-1]*a[e]

    if c.get(a[e]+1,None) != None:
        substract_left = substract_left + c[a[e]+1]*a[e]

    if c.get(a[e],None) != None:
        substract_left = substract_left + c[a[e]]*a[e]

    c[a[e]] = c[a[e]] + 1
    jsum = jsum + p[e]


add_right = 0
for e in xrange(n):
    if c.get(a[e]-1,None) != None:
        add_right = add_right + c[a[e]-1]*a[e]

    if c.get(a[e]+1,None) != None:
        add_right = add_right + c[a[e]+1]*a[e]

    if c.get(a[e],None) != None:
        c[a[e]] = c[a[e]] - 1
        add_right = add_right + (c[a[e]])*a[e]

print(jsum+add_right-substract_left)
