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. 

d={}
n=int(input())

arr=list(map(int,input().split()))
prefix=[0 for i in range(n)]
prefix[0]=arr[0]
for i in range(1,n):
    prefix[i]=prefix[i-1]+arr[i]
for i in range(1,n):
    try:
        d[arr[i]]+=1
        
    except:
        d[arr[i]]=1

s=0
for i in range(n-1):
    cnt=0
    minus=0
    if arr[i] in d:
        cnt+=d[arr[i]]
        minus=minus+d[arr[i]]*arr[i]
    if (arr[i]+1) in d:
        cnt+=d[arr[i]+1]
        minus=minus+d[arr[i]+1]*(arr[i]+1)
    if(arr[i]-1) in d:
        minus=minus+d[arr[i]-1]*(arr[i]-1)
        cnt+=d[arr[i]-1]
    s=s+prefix[n-1]-prefix[i]-minus-(n-i-1-cnt)*arr[i]
    if arr[i+1] in d:
        if (d[arr[i+1]]==1):
            d.pop(arr[i+1])
        else:
            d[arr[i+1]]-=1
print(s)