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 = []
mp = {}
for i in input().split():
	v.append(int(i))
	mp[int(i)] = 0
	mp[int(i)-1] = 0
	mp[int(i)+1] = 0
sum = 0
ele = 0
ans = 0
for i in v[::-1]:
	ans = ans + (sum - ele*i)
	a = ((i+1)*mp[i+1])-(mp[i+1]*i)
	b = ((i-1)*mp[i-1])-(mp[i-1]*i)
	ans = ans - (a+b)
	mp[i] = mp[i]+1
	sum = sum+i
	ele = ele+1
print(ans)