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

def list_output(s):    
    print(' '.join(map(str, s)))
    
def list_input(s='int'):
    if s == 'int':
        return list(map(int, input().split()))    
    elif s == 'float':
        return list(map(float, input().split()))
    return list(map(str, input().split()))

n = int(input())
a = list(map(int, input().split()))
h = dict()

tot = 0
mul = -(n-1)
for i in range(n):
    tot += mul * a[i]
    mul += 2

for i in range(n):
    if a[i] in h:
        h[a[i]] += 1
    else:
        h[a[i]] = 1
    if a[i]-1 in h:
        tot -= h[a[i]-1]
    if a[i]+1 in h:
        tot += h[a[i]+1]
print(tot)