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. 
t=int(input())
a=input().split(' ')
sum=[]
curr=0
dic={}
sum.append(0)
for i in a:
    curr=curr+int(i)
    sum.append(curr)
    if i in dic:
        p=dic[i]
        p=p+1
        dic[i]=p
    else:
        dic[i]=1

ans=0
for i in range(1,t+1):
    ans=ans+sum[t]-sum[i]-int((t-int(i)))*int(a[i-1])
    p1=str(int(a[i-1])+1)
    p2=str(int(a[i-1])-1)
    if str(p1) in dic:
        ans=ans-int(dic[str(int(a[i-1])+1)])
    if str(p2) in dic:
        ans=ans+int(dic[str(int(a[i-1])-1)])
    p=dic[a[i-1]]
    p=p-1
    dic[a[i-1]]=p
print(ans)