Let's denote a function 

<image>

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 math

n = int(input())

a = list(map(int,input().split()))

dp = [0]*n
pre = [0]*n

pre[0] = a[0]

ans,n1,p1 = 0,0,0

mp = dict()

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

for i in range(0,n):
    if a[i]-1 in mp:
        p1+=mp[a[i]-1]
        
    if a[i]+1 in mp:
        n1+=mp[a[i]+1]
        
    if a[i] in mp:
        mp[a[i]]+=1
    else:
        mp[a[i]]=1

print(ans+n1-p1)
