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 java.math.BigInteger;
import java.util.*;
import java.io.*;

public class H {
    public static void main(String[] args) throws IOException{
        BufferedReader f = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        StringTokenizer st = new StringTokenizer(f.readLine());
        int n = Integer.parseInt(st.nextToken());
        st = new StringTokenizer(f.readLine());
        long[] arr = new long[n];
        for(int i = 0; i < n; i++) arr[i] = Long.parseLong(st.nextToken());
        TreeMap<Long, Integer> cnts = new TreeMap<Long, Integer>();
        BigInteger ans = BigInteger.ZERO;
        long sum = 0;
        for(int i = 0; i < n; i++){
            update(cnts, arr[i], true);
            Long lower = cnts.lowerKey(arr[i]);
            Long higher = cnts.higherKey(arr[i]);
            if(lower != null && arr[i]-lower == 1){
                ans = ans.subtract(BigInteger.valueOf(cnts.get(lower)));
            }
            if(higher != null && higher-arr[i] == 1){
                ans = ans.add(BigInteger.valueOf(cnts.get(higher)));
            }
        }
        for(int i = 0; i < n; i++){
            sum+=arr[i];
            ans = ans.add(BigInteger.valueOf((i+1)*arr[i]-sum));
        }

        out.println(ans);
        out.close();

    }
    public static void update(TreeMap<Long, Integer> cnts, long val, boolean add){
        if(add){
            if(!cnts.containsKey(val)){
                cnts.put(val, 1);
            }else{
                cnts.put(val, cnts.get(val)+1);
            }
        }else{
            cnts.put(val, cnts.get(val)-1);
            if(cnts.get(val) == 0) cnts.remove(val);
        }
    }
}
