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())
s = input().split()
a = [int(x) for x in s]
p = [0 for i in range(len(a)+1)]
m = {}

def get(ai):
	if ai in m:
		return m[ai]
	return 0		

i = 0
for ai in a:
	p[i+1] = p[i] + ai
	if ai in m:
		m[ai] += 1
	else:
		m[ai] = 1
	i += 1
		
i = n-1
ans = 0
for ai in reversed(a):
	ans += i*ai - p[i] - get(ai-1) + get(ai+1)
	m[ai] -= 1
	i -= 1

print(ans)