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 = list(map(int, arr.split(' ')))

dict1 = {}
dict2 = {}
ans = 0

for i in range(0, N):   
    ans += i*arr[i]
    ans -= (N-i-1)*arr[i]

for i in range(0, N): 
    op1 = 0
    if( (arr[i]-1) in dict1 ):
        op1 = dict1[arr[i]-1] 
    op2 = 0
    if( (arr[i]+1) in dict1 ):
        op2 = dict1[arr[i]+1]
    op1 += op2
    ans -= (op1*arr[i])
    
    if( arr[i] in dict1 ):
       dict1[arr[i]]+=1
    else:
       dict1[arr[i]] = 1
       
for i in range(N-1, -1, -1): 
    op1 = 0
    if( (arr[i]-1) in dict2 ):
        op1 = dict2[arr[i]-1] 
    op2 = 0
    if( (arr[i]+1) in dict2 ):
        op2 = dict2[arr[i]+1]
    op1 += op2
    ans += (op1*arr[i])
    
    if( arr[i] in dict2 ):
       dict2[arr[i]]+=1
    else:
       dict2[arr[i]] = 1

print(ans)