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(input())
a=list(map(int,input().split()))
d={}
ans=0
s=0
for z in range(n):
    i=a[z]
    if i not in d:
        d[i]=0
    d[i]+=1
    count=d[i]+(d[i-1] if i-1 in d else 0)+(d[i+1] if i+1 in d else 0)
    tot=d[i]*i+(d[i-1] if i-1 in d else 0)*(i-1)+(d[i+1] if i+1 in d else 0)*(i+1)
    #print(z,count,tot,ans)
    s+=i
    ans+=i*(z-count+1)-(s-tot) 
print(ans)