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 = input()

v = map ( int , raw_input().split() )

a = {}
pref = {}

pref[0] = v[0]
for i in range ( 1 , n ) :
    pref[i] = pref[i - 1] + v[i]

h = {}
h[v[0]] = 1

ans = 0
for i in range ( 1 , n ) :
    ans += ( i * v[i] ) - pref[i - 1]

    val = v[i]
    val -= 1

    if val in h :
        ans -= h[val]

    val = v[i] + 1
    if val in h :
        ans += h[val]

    #print "i : ", i , "ans : ", ans

    if v[i] in h :
        h[v[i]] += 1
    else : 
        h[v[i]] = 1

print ( ans )

