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 get_s_in(i):
	global mp
	res = 0
	if (a[i]-1) in mp:
		res += mp[a[i]-1]*(a[i]-1)
	
	if a[i] in mp:
		res += mp[a[i]]*a[i]
	
	if (a[i]+1) in mp:
		res += mp[a[i]+1]*(a[i]+1)
	
	return res


def get_cnt_in(i):
	global mp
	res = 0
	if (a[i]-1) in mp:
		res += mp[a[i]-1]
	
	if a[i] in mp:
		res += mp[a[i]]
	
	if (a[i]+1) in mp:
		res += mp[a[i]+1]
	
	return res


n = int(input());
a = [0] + input().split()
s = [0] * (n+1)
global mp
mp = {}

for i in range(1, n+1):
	a[i] = int(a[i])
	if a[i] not in mp:
		mp[a[i]] = 1
	else:
		mp[a[i]] += 1
	s[i] = s[i-1] + a[i]

ans = 0
for i in range(n, 0, -1):
	s_in = get_s_in(i)
	cnt_in = get_cnt_in(i)
	ans += a[i] * (i - cnt_in) - (s[i] - s_in)
	mp[a[i]] -= 1

print(ans)
