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. 
def main():
	n = int(input())
	arr = list(map(int, input().split()))

	cnt = dict()
	ss = dict()
	for i in range(n):
		cnt[arr[i]] = 0
		cnt[arr[i] - 1] = 0
		cnt[arr[i] + 1] = 0
		ss[arr[i] - 1] = 0
		ss[arr[i] + 1] = 0
		ss[arr[i]] = 0

	sm = 0
	ans = 0
	for i in range(n):
		ans -= sm
		ans += i * arr[i]
		ans -= cnt[arr[i] - 1] * arr[i]
		ans -= cnt[arr[i] + 1] * arr[i]
		ans += ss[arr[i] + 1]
		ans += ss[arr[i] - 1]
		
		sm += arr[i]
		cnt[arr[i]] += 1
		ss[arr[i]] += arr[i]

	print(ans)

main()
