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. 
import sys
# sys.stdin = open('input.txt', 'r') 
# sys.stdout = open('output.txt', 'w')

n = (int)(raw_input())


a = []

a = map(int,raw_input().split(" "))

mp = dict()

sum1 = []

sum1.append(a[0])

for i in range(1,n):
	sum1.append(a[i] + sum1[i-1])
for i in range(0,n):
	if a[i] in mp:
		mp[a[i]] += 1
	else:
		mp[a[i]] = 1

# print mp
# print sum1
# print a

ans = 0

for i in range(0,n):
	if a[i]-1 in mp:
		p = mp[a[i]-1]
	else:
		p = 0
	if a[i] in mp:
		q = mp[a[i]]
	else:
		q = 0
	if a[i]+1 in mp:
		rr = mp[a[i]+1]
	else:
		rr = 0

	if i==0:
		ans1 = sum1[n-1]
	else:
		ans1 = sum1[n-1] - sum1[i-1]

	ans1 = ans1 - p*(a[i]-1)
	ans1 = ans1 - q*a[i]
	ans1 = ans1 - rr*(a[i]+1)
	ans = ans + (ans1 - (n-p-q-rr-i)*a[i])
	mp[a[i]] -= 1


print ans
