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. 
#!/usr/bin/python

import os, sys

DEBUG = os.environ.get('VHLOCAL', False) is not False

def main():
	try:
		n = int(raw_input())
	except:
		return False
	a = map(int, raw_input().split())
	
	bs = dict()
	b1 = dict()
	
	r = 0
	nbr = 0
	ts = 0
	for x in a:
		nbr0 = b1.get(x+1,0) + b1.get(x,0) + b1.get(x-1,0)
		s0 = bs.get(x+1,0) + bs.get(x,0) + bs.get(x-1,0)
		
		r += x * (nbr - nbr0) - (ts - s0)
		
		bs[x] = bs.get(x,0) + x
		b1[x] = b1.get(x,0) + 1
		
		ts += x
		nbr += 1
		
	print(r)
	
	return True

if DEBUG:
	sys.stdin = open('/tmp/in.txt', 'r')
	while main():
		pass
else:
	main()