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 get_int_list(string):
	ls = []
	sum = ''
	for s in string:
		if s == ' ':
			ls.append(int(sum))
			sum = ''
		else:
			sum += s
	ls.append(int(sum))
	return ls
	
def extras(d, num):
	plus = minus = 0
	if num + 1 in d:
		plus = d[num + 1]
	if num - 1 in d:
		minus = d[num - 1]
	return plus - minus
		
def get_ans(ls, n):
	d = {}
	sum = 0
	k = 0
	for i in ls:
		k += 1
		if i in d:
			d[i] += 1
		else:
			d[i] = 1
		sum += k * i - (n + 1 - k) * i + extras(d, i)
	return sum

		
n = int(input())
x = input()
ls = get_int_list(x)
print(get_ans(ls, n))