source_code: import java.io.BufferedReader;
  import java.io.File;
  import java.io.FileNotFoundException;
  import java.io.FileReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.math.BigInteger;
  import java.util.HashMap;
  import java.util.StringTokenizer;
  
  public class D
  {
  	public static void main(String[] args) throws IOException
  	{
  		Scanner sc = new Scanner(System.in);
  		PrintWriter pw = new PrintWriter(System.out);
  		
  		BigInteger ans = BigInteger.ZERO;
  		int n = sc.nextInt();
  		int arr[] = new int[n];
  		long cum[] = new long[n];
  		
  		for (int i = 0; i < n; i++)
  			arr[i] = sc.nextInt();
  		
  //		int n=(int)2e5;
  //		for(int i=0;i<n;i++){
  //			arr[i]=1;
  //			if(i>n/2)
  //				arr[i]=(int)1e9;
  //		}
  		
  		for (int i = 0; i < cum.length; i++)
  		{
  			cum[i] = arr[i];
  			if(i > 0)
  				cum[i] += cum[i-1];
  		}
  		
  		for (int i = 0; i < n; i++)
  			ans = ans.add(BigInteger.valueOf((1l*(i+1)*arr[i] - cum[i])));
  		
  		HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
  		for (int i = 0; i < n; i++)
  		{
  			ans =  ans.subtract(BigInteger.valueOf(map.getOrDefault(arr[i]-1, 0)));
  			ans = ans.add(BigInteger.valueOf(map.getOrDefault(arr[i]+1, 0)));
  			map.put(arr[i], map.getOrDefault(arr[i], 0)+1);
  		}
  		
  		pw.println(ans);
  		pw.flush();
  		pw.close();
  	}
  	
  		
  	static class Scanner
  	{
  		StringTokenizer st;
  		BufferedReader br;
  
  		public Scanner(InputStream s)
  		{
  			br = new BufferedReader(new InputStreamReader(s));
  		}
  
  		public Scanner(String s) throws FileNotFoundException
  		{
  			br = new BufferedReader(new FileReader(new File((s))));
  		}
  
  		public String next() throws IOException
  		{
  			while (st == null || !st.hasMoreTokens())
  				st = new StringTokenizer(br.readLine());
  			return st.nextToken();
  		}
  
  		public int nextInt() throws IOException
  		{
  			return Integer.parseInt(next());
  		}
  
  		public long nextLong() throws IOException
  		{
  			return Long.parseLong(next());
  		}
  
  		public String nextLine() throws IOException
  		{
  			return br.readLine();
  		}
  
  		public double nextDouble() throws IOException
  		{
  			String x = next();
  			StringBuilder sb = new StringBuilder("0");
  			double res = 0, f = 1;
  			boolean dec = false, neg = false;
  			int start = 0;
  			if (x.charAt(0) == '-')
  			{
  				neg = true;
  				start++;
  			}
  			for (int i = start; i < x.length(); i++)
  				if (x.charAt(i) == '.')
  				{
  					res = Long.parseLong(sb.toString());
  					sb = new StringBuilder("0");
  					dec = true;
  				} else
  				{
  					sb.append(x.charAt(i));
  					if (dec)
  						f *= 10;
  				}
  			res += Long.parseLong(sb.toString()) / f;
  			return res * (neg ? -1 : 1);
  		}
  
  		public boolean ready() throws IOException
  		{
  			return br.ready();
  		}
  	}
  }
  