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 = input().split(' ')
mp = {}
for i in range(len(a)):
	a[i] = int(a[i])
	mp[a[i]] = 0
for i in a:
	mp[i] += 1

sum = []
sum.append(a[0])
for i in range(1,len(a)):
	sum.append(sum[i-1] + a[i])

ans = 0

for i in range(0,n-1):
	cur = sum[n-1]-sum[i]
	rang = n-1-i;
	mp[a[i]] -= 1
	cur -= rang * a[i]
	cur -= mp.get(a[i]+1,0)
	cur += mp.get(a[i]-1,0)
	ans += cur

print(ans)