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();
arr = list(map(int, input().split()))
mp = {}
ans = 0
sums = 0
count = 0
for i in range(int(n)-1,-1,-1):
    sums += arr[i];
    if arr[i] in mp:
        mp[arr[i]] += 1
    else:
        mp[arr[i]] = 1
    count = count + 1;
    ans1 = 0;
    ans2 = 0;
    # print(i)
    if (arr[i]+1) in mp:
        ans1 = mp[arr[i]+1]
    if (arr[i]-1) in mp:
        ans2 = mp[arr[i]-1]   
    # print(ans1,ans2,count,arr[i])     
    ans += (sums + ans2 - ans1 - arr[i] * count);

print(ans)
