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.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Calendar;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.SortedSet;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;

/**
 * #
 * @author pttrung
 */
public class D_Edu_Round_34 {

    public static long MOD = 1000000007;

    public static void main(String[] args) throws FileNotFoundException {
        // PrintWriter out = new PrintWriter(new FileOutputStream(new File(
        // "output.txt")));
        PrintWriter out = new PrintWriter(System.out);
        Scanner in = new Scanner();
        int n = in.nextInt();
        int[] data = new int[n];
        TreeSet<Integer> set = new TreeSet<>();
        for (int i = 0; i < n; i++) {
            data[i] = in.nextInt();
            set.add(data[i]);
        }
        int index = 0;
        HashMap<Integer, Integer> map = new HashMap<>();
        HashMap<Integer, Integer> rev = new HashMap<>();
        for (int i : set) {
            map.put(i, index);
            rev.put(index, i);
            index++;
        }
        Node root = new Node(0, index);
        BigInteger result = BigInteger.ZERO;
        //System.out.println(rev + " " + map);
        for (int i = 0; i < n; i++) {
            int cur = map.get(data[i]);
            long v = data[i];
            update(cur, data[i], root);
            if (cur > 0) {
                int less = cur - 1;
                if (rev.get(less) + 1 == data[i]) {
                    less--;
                }
                //System.out.println(rev.get(less) + " " + less + " " + cur);
                if (less >= 0) {
                    Re tmp = get(0, less, root);
                    //System.out.println("Less " + tmp.count + " " + tmp.total + " " + i);
                    result = result.add(BigInteger.valueOf(tmp.count).multiply(BigInteger.valueOf(v)).subtract(BigInteger.valueOf(tmp.total)));
                }
            }
            if (cur + 1 < index) {
                int more = cur + 1;
                if (rev.get(more) == data[i] + 1) {
                    more++;
                }
                if (more < index) {
                    Re tmp = get(more, index, root);
                    //System.out.println("More " + tmp.count + " " + tmp.total + " " + i);
                    result = result.add(BigInteger.valueOf(tmp.count).multiply(BigInteger.valueOf(v)).subtract(BigInteger.valueOf(tmp.total)));
                }
            }
        }
        out.println(result);
        out.close();
    }

    static Re get(int l, int r, Node node) {
        if (node.l > r || node.r < l) {
            return new Re();
        }
        Re result = new Re();
        if (l <= node.l && node.r <= r) {
            result.total = node.total;
            result.count = node.count;
            return result;
        }
        if (node.left != null) {
            Re a = get(l, r, node.left);
            Re b = get(l, r, node.right);
            result.total = a.total + b.total;
            result.count = a.count + b.count;
        }
        return result;

    }

    static void update(int index, int val, Node node) {
        if (node.l > index || node.r < index) {
            return;
        }
        if (node.l == index && node.r == index) {
            node.count++;
            node.total += val;
            return;
        }
        if (node.left == null) {
            int mid = (node.l + node.r) / 2;
            node.left = new Node(node.l, mid);
            node.right = new Node(mid + 1, node.r);
        }
        update(index, val, node.left);
        update(index, val, node.right);
        node.total = node.left.total + node.right.total;
        node.count = node.left.count + node.right.count;
    }

    static class Re {

        long total = 0;
        long count = 0;

    }

    static class Node {

        int l, r;
        long total = 0;
        long count = 0;
        Node left, right;

        Node(int l, int r) {
            this.l = l;
            this.r = r;
        }
    }

    public static int[] KMP(String val) {
        int i = 0;
        int j = -1;
        int[] result = new int[val.length() + 1];
        result[0] = -1;
        while (i < val.length()) {
            while (j >= 0 && val.charAt(j) != val.charAt(i)) {
                j = result[j];
            }
            j++;
            i++;
            result[i] = j;
        }
        return result;

    }

    public static boolean nextPer(int[] data) {
        int i = data.length - 1;
        while (i > 0 && data[i] < data[i - 1]) {
            i--;
        }
        if (i == 0) {
            return false;
        }
        int j = data.length - 1;
        while (data[j] < data[i - 1]) {
            j--;
        }
        int temp = data[i - 1];
        data[i - 1] = data[j];
        data[j] = temp;
        Arrays.sort(data, i, data.length);
        return true;
    }

    public static int digit(long n) {
        int result = 0;
        while (n > 0) {
            n /= 10;
            result++;
        }
        return result;
    }

    public static double dist(long a, long b, long x, long y) {
        double val = (b - a) * (b - a) + (x - y) * (x - y);
        val = Math.sqrt(val);
        double other = x * x + a * a;
        other = Math.sqrt(other);
        return val + other;

    }

    public static class Point implements Comparable<Point> {

        int x, y;

        public Point(int start, int end) {
            this.x = start;
            this.y = end;
        }

        @Override
        public int hashCode() {
            int hash = 5;
            hash = 47 * hash + this.x;
            hash = 47 * hash + this.y;
            return hash;
        }

        @Override
        public boolean equals(Object obj) {
            if (obj == null) {
                return false;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            final Point other = (Point) obj;
            if (this.x != other.x) {
                return false;
            }
            if (this.y != other.y) {
                return false;
            }
            return true;
        }

        @Override
        public int compareTo(Point o) {
            return Integer.compare(x, o.x);
        }
    }

    public static class FT {

        long[] data;

        FT(int n) {
            data = new long[n];
        }

        public void update(int index, long value) {
            while (index < data.length) {
                data[index] += value;
                index += (index & (-index));
            }
        }

        public long get(int index) {
            long result = 0;
            while (index > 0) {
                result += data[index];
                index -= (index & (-index));
            }
            return result;

        }
    }

    public static long gcd(long a, long b) {
        if (b == 0) {
            return a;
        }
        return gcd(b, a % b);
    }

    public static long pow(long a, long b, long MOD) {
        if (b == 0) {
            return 1;
        }
        if (b == 1) {
            return a;
        }
        long val = pow(a, b / 2, MOD);
        if (b % 2 == 0) {
            return val * val % MOD;
        } else {
            return val * (val * a % MOD) % MOD;

        }
    }

    static class Scanner {

        BufferedReader br;
        StringTokenizer st;

        public Scanner() throws FileNotFoundException {
            // System.setOut(new PrintStream(new BufferedOutputStream(System.out), true));
            br = new BufferedReader(new InputStreamReader(System.in));
            //  br = new BufferedReader(new InputStreamReader(new FileInputStream(new File("input.txt"))));
        }

        public String next() {

            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    throw new RuntimeException();
                }
            }
            return st.nextToken();
        }

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

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

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

        public String nextLine() {
            st = null;
            try {
                return br.readLine();
            } catch (Exception e) {
                throw new RuntimeException();
            }
        }

        public boolean endLine() {
            try {
                String next = br.readLine();
                while (next != null && next.trim().isEmpty()) {
                    next = br.readLine();
                }
                if (next == null) {
                    return true;
                }
                st = new StringTokenizer(next);
                return st.hasMoreTokens();
            } catch (Exception e) {
                throw new RuntimeException();
            }
        }
    }
}
