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 = input()
um = {}
a = map(int, raw_input().split())
a = [-13] + a
suf = [0] * (n + 13)
for ele in a:
	if ele in um:
		um[ele] += 1
	else:
		um[ele] = 1
for i in range(n, 0, -1):
	suf[i] = suf[i + 1] + a[i]
res = 0
for i in range(1, n + 1):
	res += suf[i];
	excl = 0
	gr = a[i] + 1
	sm = a[i] - 1
	if gr in um:
		excl += um[gr]
		res -= um[gr] * gr
	if sm in um:
		excl += um[sm]
		res -= um[sm] * sm
	res -= (n - i + 1 - excl) * a[i]
	um[a[i]] -= 1
print res
