Let's denote a function 

<image>

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())
s = input().split()
a = [int(i) for i in s]
m1 = {}
m2 = {}
sum = 0
def get(m, a):
    if a in m:
        return m[a]
    else:
        return 0

ans = 0
for i in range(n):
    ans += i * a[i] - sum + get(m1, a[i]) - get(m2, a[i])
    if not ((a[i] - 1) in m1):
        m1[a[i] - 1] = 0
    if not ((a[i] + 1) in m2):
        m2[a[i] + 1] = 0
    m1[a[i] - 1] += 1
    m2[a[i] + 1] += 1
    sum += a[i]
print(ans)