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())
arr=input()
arr=arr.split()
for i in range(n):
    arr[i]=int(arr[i])
ans=0
sm=arr[0]
m={}
m[sm]=1
for i in range(1,n):
    a=0
    b=0
    c=0
    d=0
    x=arr[i]
    if not x in m:
        m[x]=0
    m[x]+=1
    if x-1 in m:
        a=m[x-1]
    if x+1 in m:
        b=m[x+1]
    ans = ans + x*(i-a-b) - (sm - a*(x-1) - b*(x+1))
    sm += x;
print(ans)
