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. 
import bisect
src=input()
n=int(src)

def consum(x):
    data=x[:]
    for i in range(1,len(data)):
        data[i]+=data[i-1]

    return data

src=input()
a=list([0])
a.extend(list( map(int,src.split() )))

pro=consum(a)

res=0
ma={}
for i in range(1,n+1):
    if(ma.get(a[i])):
        ma[a[i]]+=1
    else:
        ma[a[i]]=1
    
    res+=(i-1)*a[i]-pro[i-1]

    if(ma.get(a[i]-1)):
        res-=ma[a[i]-1]
    if(ma.get(a[i]+1)):
        res+=ma[a[i]+1]
    
print(res)
