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 query(l, r):
	return s[r] - s[l - 1]

n = int(input())
a = [0] + [int(i) for i in input().split()]

s = [0 for i in range(n + 1)]

for i in range(1, n + 1):
	s[i] = s[i - 1] + a[i]

ans = 0
m = {}

for i in range(n, 0, -1):
	ans += query(i + 1, n) - (n - i) * a[i]

	if a[i] + 1 in m:
		ans -= m[a[i] + 1];

	if a[i] - 1 in m:
		ans += m[a[i] - 1];
		
	if a[i] in m:
		m[a[i]] += 1
	else:
		m[a[i]] = 1

print(ans)