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 = raw_input()
str_arr = raw_input().split(' ')
arr = [int(num) for num in str_arr]
n=int(n)

vals = dict()
vals[0]=0
vals[1]=0
ans = 0
for i in range(1,n) :
    vals[i] = vals[i-1] + arr[i-1] - (i)*arr[i] 
    if i >= 2 :
        vals[i] = vals[i] + (i-1)*arr[i-1] 
    ans += vals[i]
val = dict()

for i in range(0,n) :
    if arr[i] in val :
        val[arr[i]] = val[arr[i]] + 1
    else :
        val[arr[i]] = 1
    if arr[i]-1 in val :
        ans = ans + val[arr[i]-1]
    if arr[i]+1 in val :
        ans = ans - val[arr[i] + 1]
ans = -1*ans
print ans;
