Let's denote a function 

<image>

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

public class Main {

    static class Task {

        void solve(int test, FastScanner in, PrintWriter out) {
            int n = in.nextInt();
            long[] a = new long[n];
            for (int i = 0; i < n; i++) {
                a[i] = in.nextInt();
            }

            BigInteger res = BigInteger.ZERO;
            for (int i = n - 1; i >= 0; i--) {
                res = res.add(BigInteger.valueOf(i * a[i] - (n - 1 - i) * a[i]));
            }

            HashMap<Long, Long> map = new HashMap<>();
            for(int i = 0; i < n; i++) {
                res = res.subtract(BigInteger.valueOf(map.getOrDefault(a[i] - 1, 0L)));
                res = res.add(BigInteger.valueOf(map.getOrDefault(a[i] + 1, 0L)));
                map.put(a[i], map.getOrDefault(a[i], 0L) + 1);
            }

            out.println(res);
        }
    }

    public static void main(String[] args) throws IOException {
        FastScanner in = new FastScanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
//        FastScanner in = new FastScanner("arithm.in");
//        PrintWriter out = new PrintWriter(new FileWriter("arithm.out"));
        new Task().solve(1, in, out);
        out.close();
    }

    static class FastScanner {
        BufferedReader br;
        StringTokenizer token;

        public FastScanner(InputStream is) {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        public FastScanner(String s) {
            try {
                br = new BufferedReader(new FileReader(s));
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
        }

        public String nextToken() {
            while (token == null || !token.hasMoreTokens()) {
                try {
                    token = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return token.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(nextToken());
        }

        public long nextLong() {
            return Long.parseLong(nextToken());
        }

        public double nextDouble() {
            return Double.parseDouble(nextToken());
        }
    }
}