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())
v = list(map(int, input().split()))
m={}
res=0

for i in v:
     if not i in m:
          m[i]=0
     m[i]+=1
     
k=v.copy()

for i in range(n-1,0,-1):
     k[i-1]=k[i]+k[i-1]
     
for i in range(0,n-1):
     res += -(n-i-1)*v[i]+k[i+1]
     m[v[i]]-=1
     if v[i]+1 in m:
          res-=m[v[i]+1]
     if v[i]-1 in m:
          res+=m[v[i]-1]

print(res)