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. 
from itertools import accumulate
def cald(left,right):
    i=0
    j=0
    ans=0
    l1=len(left)
    l2=len(right)
    while j<len(right):
        while i<l1 and left[i]<right[j]:
            i+=1
        ans+=l1-2*i
        j+=1
    return ans
            

n=int(input())
a=list(map(int,input().split()))
dict={}
for i in range(n):
    if a[i] not in dict:
        dict[a[i]]=[]
    dict[a[i]].append(i)

ks=list(dict.keys())
ans=0

for x in ks:
    if x-1 in dict:
        ans+=cald(dict[x-1],dict[x])
pre=list(accumulate(a))

for i in range(1,n):
    ans+=i*a[i]-pre[i-1]
    

print(ans)
        
     