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 atexit, io, sys, collections, math, heapq
buffer = io.BytesIO() 
sys.stdout = buffer
@atexit.register 
def write(): sys.__stdout__.write(buffer.getvalue())   


#10 6 100
#17 5
#4
#4 2 4 3

n,ais = int(raw_input()), map(int, raw_input().split())
cc = collections.Counter()

s = 0
ans  =0 
for j,aj in enumerate(ais):

	ans += j * aj
	ans -= s

	ans -= cc[aj + 1] * (aj)
	ans += cc[aj + 1] * (aj + 1)

	ans -= cc[aj - 1] * (aj)
	ans += cc[aj - 1] * (aj - 1)
	

	s += aj
	cc[aj]+=1

print ans