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. 
a=int(input())
arr=list(map(int,input().split()))
d=dict()
summ=[0]
brr=arr
nd=dict()
mimpp=dict()
mimpn=dict()
for i in arr:
    summ.append(i+summ[len(summ)-1])
    if(i in d):
        d[i]=d[i]+1
    else:
        d[i]=1
for i in range(0,len(brr)):
    if(brr[i] in nd):
        nd[brr[i]]=nd[brr[i]]+1
    else:
        nd[brr[i]]=1
    mimpn[i]=0
    mimpp[i]=0
    if(brr[i]-1 in d):
        mimpn[i]=mimpn[i]+d[brr[i]-1]
    if(brr[i]+1 in d):
        mimpp[i]=mimpp[i]+d[brr[i]+1]
    if(brr[i]-1 in nd):
        mimpn[i]=mimpn[i]-nd[brr[i]-1]
    if(brr[i]+1 in nd):
        mimpp[i]=mimpp[i]-nd[brr[i]+1]
    
ans=0
ind=0
su=sum(arr)
for i in range(0,len(arr)):
    ans=ans+su-summ[ind]-(a-ind)*arr[i]
    ans=ans+mimpn[i]  
    ans=ans-mimpp[i]   
    ind=ind+1 
print(ans)
