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. 
'''input
4
6 6 4 4
'''

def list_input():
    return list(map(int,input().split()))
def map_input():
    return map(int,input().split())
def map_string():
    return input().split()

ans = 0
d = {}
cnt = 0
n = int(input())
a = list_input()
for i in range(n):
	tot = i 
	cur = cnt
	if a[i] in d:
		tot -= d[a[i]]
		cur -= a[i]*d[a[i]]
	if a[i]-1 in d: 
		tot -= d[a[i]-1]
		cur -= d[a[i]-1]*(a[i]-1)
	if a[i]+1 in d: 
		tot -= d[a[i]+1]
		cur -= d[a[i]+1]*(a[i]+1)
	ans += tot*a[i]-cur;
	cnt += a[i];
	if a[i] not in d: d[a[i]] = 1
	else: d[a[i]] += 1
print(ans)	
