Let's denote a function 

<image>

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. 
#!/usr/bin/python

n = map(int, raw_input().split())[0];
a = map(int, raw_input().split());
a = [0] + a
#print (n)
#print (a)
pre_sum = [0 for i in range(len(a))]
m = {};
for i in range(1, len(a)):
	pre_sum[i] = pre_sum[i - 1] + a[i]
	if (a[i] not in m):
		m[a[i]] = 1
	else:
		m[a[i]] = m[a[i]] + 1

#print (m)
ans = 0
i = len(a) - 1

while i > 0:
	m[a[i]] -= 1
	if (a[i] + 1) in m:
		plus = m[a[i] + 1]
	else:
		plus = 0
	if (a[i] - 1) in m:
		sub = m[a[i] - 1]
	else:
		sub = 0
	ans += i * a[i] - pre_sum[i] + plus - sub;
	i -= 1
print (ans)
