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. 
from sys import stdin
from collections import Counter

n = int(stdin.readline())
v = list(map(int, stdin.readline().split()))

cnt = Counter()

sum = 0
for i in range(n):
	sum += v[i]
	cnt[ v[i] ] += 1

ans = 0
for i in range(n):
	tmp = sum - v[i] * cnt[ v[i] ] - (v[i]-1) * cnt[ v[i]-1 ] - (v[i]+1) * cnt[ v[i]+1 ]
	t = n - i - cnt[ v[i] ] - cnt[ v[i]-1 ] - cnt[ v[i]+1 ]
	ans += tmp - t * v[i]
	
	cnt[ v[i] ] -= 1
	sum -= v[i]

print (ans)