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. 
#!/bin/bash

cnt = {}

n = int(input())

tot_sum = 0
tot_cnt = 0
res = 0

for y in input().split():
	y = int(y)
	tot_sum += y
	tot_cnt += 1

	if y in cnt:
		cnt[y] += 1
	else:
		cnt[y] = 1

	tmp_sum = tot_sum
	tmp_cnt = tot_cnt

	for d in range(-1, 2):
		x = y + d
		if x in cnt:
			tmp_sum -= x * cnt[x]
			tmp_cnt -= cnt[x]

	res += tmp_cnt * y - tmp_sum


print(res)
