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. 


occ = {}


n = int(input())

v = map(int,raw_input().split())
ssum = [0] * n

for i in range(n):

	x = v[i]
	if(x in occ):
		occ[x] = occ[x] + 1
	else:
		occ[x] = 1
acc = 0
for i in range(n-1,-1,-1):
	acc += v[i]
	ssum[i] = acc




ans = 0
for i in range(n-1):
	occ[v[i]] = occ[v[i]] - 1

	if(v[i]-1 not in occ):
		occ[v[i]-1] = 0
	if(v[i]+1 not in occ):
		occ[v[i]+1] = 0
	val = ssum[i+1]
	val -= occ[v[i]] * v[i]
	val -= occ[v[i]-1] * (v[i]-1)
	val -= occ[v[i]+1] * (v[i]+1)

	hm = n - i - 1 - (occ[v[i]] + occ[v[i]+1] + occ[v[i]-1])
	

	ans += val - (hm * v[i])


print(ans)
