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 sys

f = sys.stdin.read().split()
n = int(f[0])
a = map(int, f[1:])

csum = [0]
for i in range(n):
    csum.append(csum[i]+a[i])

res = 0
for i in range(n):
    res += (csum[n]-csum[i]) - (n-i)*a[i]

counts = {}

for i in range(n):
    for x in [a[i]-1, a[i]+1]:
        if (x not in counts):
            counts[x]=0
        res -= (a[i]-x)*counts[x]
       #print "Removing:", i, a[i], x, (a[i]-x)*counts[x]
    if a[i] not in counts:
        counts[a[i]]=0
    counts[a[i]] += 1
        
print res
