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 fractions import gcd
from math import factorial, ceil, sqrt, atan2
from itertools import *
import string
import copy
import random
from decimal import *
import bisect
def id_generator(size=20, chars=string.digits):
    return ''.join(random.choice(chars) for _ in range(size))
 
def mp():
    return map(int,str(raw_input()).split())

n=input()
l=list(mp())
d={}
ans=0
s=sum(l)
for i in range(n):	
	try:
		if d[l[i]]:
			d[l[i]]+=1
	except:
		d[l[i]]=1
bla=n
#print d
for i in range(n):
	pre=bla
	tot=s
	try:
		if d[l[i]+1]:
			tot-=(l[i]+1)*d[l[i]+1]
			pre-=d[l[i]+1]
	except:
		pass

	try:
		if d[l[i]-1]:
			tot-=(l[i]-1)*d[l[i]-1]
			pre-=d[l[i]-1]
	except:
		pass

	try:
		if d[l[i]]:
			tot-=l[i]*d[l[i]]
			pre-=d[l[i]]
	except:
		pass
	ans+=tot
	ans-=pre*l[i]
	bla-=1
	d[l[i]]-=1
	s-=l[i]
	#print ans,tot,pre,d,s,l[i]
print ans
