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(raw_input())
a = [int(x) for x in raw_input().split(' ')]

sum_all = 0
res = 0
mp = {}

def get(u):
    if u in mp:
        return mp[u]
    return 0

def incr(u):
    if u in mp:
        mp[u] += 1
    else:
        mp[u] = 1
        
for i in xrange(n - 1, -1, -1):
    res += sum_all - (n - 1 - i) * a[i];
    res -= get(a[i] - 1) * (-1);
    res -= get(a[i] + 1) * (1);
    sum_all += a[i];
    incr(a[i])

print res
