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 almostDifference(nums):

	ht = {}
	result = 0
	prefix_sum = 0

	# y is nums[i], x is all elements before it
	for i, n in enumerate(nums):
		ht.setdefault(n, 0)
		ht.setdefault(n-1, 0)
		ht.setdefault(n+1, 0)

		result -= prefix_sum	# subtract all the x's
		result += n*(i)			# add y (i+1) times
		result -= ht[n-1]*1		# remove the bonus (+)
		result -= ht[n+1]*-1	# remove the bonus (-)

		ht[n] += 1
		prefix_sum += n

	return result




_ = int(input())
nums = [int(x) for x in input().split()]
print(almostDifference(nums))