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. 
//>>>BaZ<<<//
import java.util.*;
import java.io.*;
import static java.lang.Math.*;
import java.math.BigInteger;
public class Main
{  
    static int dx[] = {-1,1,0,0};
    static int dy[] = {0,0,1,-1};
    static long MOD = 1000000007;
    static int INF = Integer.MAX_VALUE/10;
    static PrintWriter pw;
    static Reader scan;
    //static MyFileReader scan;
    //static MyFileReader1 ss;
    static int ni() throws IOException{return scan.nextInt();}
    static long nl() throws IOException{return scan.nextLong();}
    static double nd() throws IOException{return scan.nextDouble();}
    static void pl() throws IOException{pw.println();}
    static void pl(Object o) throws IOException{pw.println(o);}
    static void p(Object o) throws IOException {pw.print(o+" ");}
    static void psb(StringBuilder sb) throws IOException {pw.print(sb);}
    static Map<Integer,Integer> map = new HashMap();
    public static void main(String[] args){
        new Thread(null,null,"BaZ",99999999)
        {
            public void run()
            {
                try
                {
                    solve();
                }
                catch(Exception e)
                {  
                    e.printStackTrace();
                    System.exit(1);
                }
            }
        }.start();
    }
    static void solve() throws IOException
    {  
        Calendar CAL1 = Calendar.getInstance();
        CAL1.setTime(new Date());
        scan = new Reader();
        //scan = new MyFileReader();
        //ss = new MyFileReader1();
        pw = new PrintWriter(System.out,true);
        //pw = new PrintWriter(new File("C://Users/Aman deep/Desktop/output.txt"));  
        StringBuilder sb = new StringBuilder();
        int n = ni();
        BigInteger ans = BigInteger.ZERO;
        BigInteger psum = BigInteger.ZERO;
        //Map<Integer,Integer> map = new HashMap();
        for(int i=1;i<=n;++i)
        {
            int temp = ni();
            add(temp);
            psum = psum.add(BigInteger.valueOf(temp));
            long x = 1L*temp*i;
            ans = ans.add(BigInteger.valueOf(x));
            ans =  ans.subtract(psum);
            Integer a1 = map.get(temp-1);
            if(a1!=null)
                ans = ans.subtract(BigInteger.valueOf(a1));
            Integer a2 = map.get(temp+1);
            if(a2!=null)
                ans = ans.add(BigInteger.valueOf(a2));
        }
        pl(ans);
        Calendar CAL2 = Calendar.getInstance();
        CAL2.setTime(new Date());
        double Execution_Time = (double)(CAL2.getTimeInMillis()-CAL1.getTimeInMillis())/1000.000;
        //System.out.println("Execution time : "+Execution_Time+" seconds");
        pw.flush();
        pw.close();
    }
    static void add(int val)
    {
        Integer corr = map.get(val);
        if(corr!=null)
            map.put(val,corr+1);
        else map.put(val,1);
    }
    static boolean islong(double d)
    {
        return Math.ceil(d)==d;
    }
    static double roundLikeCpp(double d,double precision)
    {   
        if(islong(d))
            return d;
        d*=(long)pow(10,precision+1);
        if(d%10==5)
            d--;
        return d/pow(10,precision+1);
    }
    static class Reader {
    final private int BUFFER_SIZE = 1 << 16;
    private DataInputStream din;
    private byte[] buffer;
    private int bufferPointer, bytesRead;

    public Reader() {
        din = new DataInputStream(System.in);
        buffer = new byte[BUFFER_SIZE];
        bufferPointer = bytesRead = 0;
    }

    public Reader(String file_name) throws IOException {
        din = new DataInputStream(new FileInputStream(file_name));
        buffer = new byte[BUFFER_SIZE];
        bufferPointer = bytesRead = 0;
    }

    public String readLine() throws IOException {
        byte[] buf = new byte[64];
        int cnt = 0, c;
        while ((c = read()) != -1) {
            if (c == '\n') break;
            buf[cnt++] = (byte) c;
        }
        return new String(buf, 0, cnt);
    }

    public int nextInt() throws IOException {
        int ret = 0;
        byte c = read();
        while (c <= ' ') c = read();
        boolean neg = (c == '-');
        if (neg) c = read();
        do {
            ret = ret * 10 + c - '0';
        } while ((c = read()) >= '0' && c <= '9');
        if (neg) return -ret;
        return ret;
    }

    public long nextLong() throws IOException {
        long ret = 0;
        byte c = read();
        while (c <= ' ') c = read();
        boolean neg = (c == '-');
        if (neg) c = read();
        do {
            ret = ret * 10 + c - '0';
        } while ((c = read()) >= '0' && c <= '9');
        if (neg) return -ret;
        return ret;
    }

    public double nextDouble() throws IOException {
        double ret = 0, div = 1;
        byte c = read();
        while (c <= ' ') c = read();
        boolean neg = (c == '-');
        if (neg) c = read();
        do {
            ret = ret * 10 + c - '0';
        } while ((c = read()) >= '0' && c <= '9');
        if (c == '.') while ((c = read()) >= '0' && c <= '9') ret += (c - '0') / (div *= 10);
        if (neg) return -ret;
        return ret;
    }

    private void fillBuffer() throws IOException {
        bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
        if (bytesRead == -1) buffer[0] = -1;
    }

    private byte read() throws IOException {
        if (bufferPointer == bytesRead) fillBuffer();
        return buffer[bufferPointer++];
    }

    public void close() throws IOException {
        if (din == null) return;
        din.close();
    }
}
     static class MyFileReader                                          //File input template
    {
        StringTokenizer st;
        BufferedReader br;
        MyFileReader() throws IOException
        {
            br = new BufferedReader(new FileReader("C://Users/Aman deep/Desktop/input.txt"));
        }
        String nextLine() throws IOException
        {
            return br.readLine();
        }
        String next() throws IOException
        {
            if(st==null || !st.hasMoreTokens())
                st = new StringTokenizer(nextLine());
            return st.nextToken();
        }
        int nextInt() throws IOException
        {
            return Integer.parseInt(next());
        }
        long nextLong() throws IOException
        {
            return Long.parseLong(next());
        }
        double nextDouble() throws IOException
        {
            return Double.parseDouble(next());
        }
    }
     static class MyFileReader1                                          //File input template
    {
        StringTokenizer st;
        BufferedReader br;
        MyFileReader1() throws IOException
        {
            br = new BufferedReader(new FileReader("C://Users/Aman deep/Desktop/output.txt"));
        }
        String nextLine() throws IOException
        {
            return br.readLine();
        }
        String next() throws IOException
        {
            if(st==null || !st.hasMoreTokens())
                st = new StringTokenizer(nextLine());
            return st.nextToken();
        }
        int nextInt() throws IOException
        {
            return Integer.parseInt(next());
        }
        long nextLong() throws IOException
        {
            return Long.parseLong(next());
        }
        double nextDouble() throws IOException
        {
            return Double.parseDouble(next());
        }
    }
}
