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.util.*;
import java.io.*;
import java.math.*;
public class Main{
    static final long MOD = (long)1e9+7;
    static FastReader in;
    public static void main(String[] args){
        in = new FastReader();
        int n = ni();
        HashMap<Long, Integer> map = new HashMap<>();
        BigInteger ans = BigInteger.ZERO;
        long[] ar = new long[n];
        int[] count = new int[n+1], count1 = new int[n+1];
        int cur = 1;
        for(int i = 0; i< n; i++){
            ar[i] = nl();
            if(!map.containsKey(ar[i]))map.put(ar[i], cur++);
            count[(int)map.get(ar[i])]++;
        }
        for(int i = 0; i< n; i++){
            int i1 = map.getOrDefault(ar[i]-1, 0), i2 = map.getOrDefault(ar[i]+1,0), i3 = map.get(ar[i]);
            int c1 = count1[i1]+count1[i2]+count1[i3];
            int c2 = count[i1]+count[i2]+count[i3]-1-c1;
            c1 = i-c1;
            c2 = n-i-1-c2;
            ans = ans.add(BigInteger.valueOf((c1-c2)*ar[i])); 
            count1[i3]++;
        }
        pn(ans.toString());
    }
    
    static void p(Object o){
        System.out.print(o);
    }
    
    static void pn(Object o){
        System.out.println(o);
    }
    
    static String n(){
        return in.next();
    }
    
    static String nln(){
        return in.nextLine();
    }
    
    static int ni(){
        return Integer.parseInt(in.next());
    }
    
    static int[] ia(int N){
        int[] a = new int[N];
        for(int i = 0; i<N; i++)a[i] = ni();
        return a;
    }
    
    static long[] la(int N){
        long[] a = new long[N];
        for(int i = 0; i<N; i++)a[i] = nl();
        return a;
    }
    
    static long nl(){
        return Long.parseLong(in.next());
    }
    
    static double nd(){
        return Double.parseDouble(in.next());
    }
    
    static class FastReader{
        BufferedReader br;
        StringTokenizer st;
        public FastReader(){
            br = new BufferedReader(new InputStreamReader(System.in));
        }
 
        String next(){
            while (st == null || !st.hasMoreElements()){
                try{
                    st = new StringTokenizer(br.readLine());
                }catch (IOException  e){
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
 
        String nextLine(){
            String str = "";
            try{
                str = br.readLine();
            }catch (IOException e){
                e.printStackTrace();
            }
            return str;
        }
    }
} 