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(x) for x in input().split()]
m1 = {-1:-1}
m2 = {-1:-1}
ans = 0
for i in range(n):
  x, y, z = 0, 0, 0
  if a[i] in m1:
    x = m1[a[i]]
  if a[i]-1 in m1:
    y = m1[a[i]-1]
  if a[i]+1 in m1:
    z = m1[a[i]+1]
  ans = ans + a[i]*(i-x-y-z)
  m1[a[i]] = x+1
for i in range(n):
  x, y, z = 0, 0, 0
  if a[n-1-i] in m2:
    x = m2[a[n-1-i]]
  if a[n-1-i]-1 in m2:
    y = m2[a[n-1-i]-1]
  if a[n-1-i]+1 in m2:
    z = m2[a[n-1-i]+1]
  ans = ans - a[n-1-i]*(i -x-y-z)
  m2[a[n-1-i]] = x+1
print(ans)
    