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. 
from bisect import bisect

n = int(input())
a = [int(i) for i in input().split()]
cnt = 0
for i in range(n):
	cnt += a[i]*i
	cnt -= a[i]*(n-i-1)
m = {}
for i in range(n):
	if a[i] not in m:
		m[a[i]] = []
	m[a[i]].append(i)

l = sorted([(i,m[i]) for i in m])

fix = 0
for i in range(len(l)-1):
	if abs(l[i][0]-l[i+1][0])==1:
		tmp = 0
		for i0 in l[i][1]:
			i1 = bisect(l[i+1][1],i0)
#			print('i1=%d,e=%d'%(i1,i0))
			tmp = tmp + len(l[i+1][1]) - 2 * i1
#		print(tmp)
		if l[i][0]<l[i+1][0]:
			fix = fix + tmp
		else:
			fix = fix - tmp
#print(l)
#print('fix',fix)
#print('cnt',cnt)
print(cnt-fix)
