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. 
# Chaitanya Bhutada 
import math
import collections
import bisect
import heapq
import time
import random
import itertools
import sys

n = int(input())
mp = {}
F = [0]*200009
F = list(map(int,input().split()))
ans = 0
see = -(n-1)

for i in range(n):
	ans=ans+see*F[i]
	see=see+2
	
for i in range(n):
        j=n-i-1   
        gN=mp.get(F[j]+1)
        if(gN==None):
        	gN=0
        lN=mp.get(F[j]-1)
        if(lN==None):
        	lN=0
        ans=ans+lN-gN
        val=mp.get(F[j])	
        if(val==None):
        	val=0
        val=val+1
        mp[F[j]]=val
print(ans);
		
