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. 
from collections import defaultdict
n = int(raw_input().strip())
a = map(int, raw_input().strip().split())
s = [0]*n
s[0] = a[0]
for i in xrange(1, n):
    s[i] = s[i-1] + a[i]
cnt = defaultdict(lambda:0)
ans = 0
for i in xrange(0, n):
    ans -= (a[i]*(i))
    if i > 0:
        ans += s[i-1]
    ans -= (cnt[a[i]-1]*(a[i]-1))
    ans -= (cnt[a[i]]*(a[i]))
    ans -= (cnt[a[i]+1]*(a[i]+1))
    ans += ((cnt[a[i]-1] + cnt[a[i]] + cnt[a[i]+1])*a[i])
    cnt[a[i]] += 1
print -ans
