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())

a = list(map(int, input().split()))
cnt = 0;
m = dict()
s = 0
ans = 0

for i in a:
	m[i] = 0
	m[i - 1] = 0
	m[i + 1] = 0

for i in range(n - 1, -1, -1):
	ans += s - cnt * a[i];
	for j in range(-1, 2):
		ans -= m[a[i] + j] * ((a[i] + j) - a[i]);
	# // dbg(i, ans);
	s += a[i];
	m[a[i]] += 1;
	cnt += 1;

print(ans)

# // 9 999 999 990 000 000 000