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. 
n=int(raw_input())
N=map(int,raw_input().split())
s=[N[0]]
for i in range(1,n):
	s.append(s[i-1]+N[i])
d={}
for i in N:
	if i not in d:
		d[i]=1
	else:
		d[i]+=1
ans=0
for j in range(n):
	res=cnt=0
	for k in range(-1,2):
		if N[j]+k in d:
			res+=d[N[j]+k]*(N[j]+k)
			cnt+=d[N[j]+k]
	su=s[n-1]
	if j!=0:
		su-=s[j-1]
	ans+=(su-res-(n-cnt-j)*N[j])
	d[N[j]]-=1
print ans
