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 set(x) : 
	if(x not in m) : 
		m[x] = 0

n = int(input())
a = list(map(int, input().split()))
m = {}
ans, total = 0, 0

for i in range(0, n) : 
	x = a[i]; 
	set(x), set(x - 1), set(x + 1)
	ans = ans + (i - m[x] - m[x - 1] - m[x + 1]) * x; 
	ans = ans -(total - m[x] * x - m[x - 1] * (x - 1) - m[x + 1] * (x + 1)); 

	m[x], total = m[x] + 1, total + x

print(ans) 