source_code: /* package whatever; // don't place package name! */
  
  import java.util.*;
  import java.lang.*;
  import java.io.*;
  import java.math.*;
  
  /* Name of the class has to be "Main" only if the class is public. */
  public class Main
  {
  	public static void main (String[] args) throws java.lang.Exception
  	{
  		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
  		int n=Integer.parseInt(br.readLine());
  		int[] A=new int[n];
  		String[] s=br.readLine().split(" ");
  		for(int i=0;i<n;i++){
  			A[i]=Integer.parseInt(s[i]);
  		}
  		Map memo=new HashMap();
  		int[] f=new int[n];
  		for(int i=0;i<n;i++){
  			if(!memo.containsKey(A[i])){
  				memo.put(A[i],1);
  			}
  			else{
  				int ct=(int)memo.get(A[i]);
  				memo.put(A[i],ct+1);
  			}
  			int tot=0;
  			if(memo.containsKey(A[i]-1)){
  				tot+=(int)memo.get(A[i]-1);
  			}
  			if(memo.containsKey(A[i]+1)){
  				tot+=(int)memo.get(A[i]+1);
  			}
  			tot+=(int)memo.get(A[i]);
  			f[i]=tot;
  		}
  		BigInteger res=new BigInteger("0");
  		for(int i=0;i<n;i++){
  			int tot1=i+1-f[i];
  			int tot2=0;
  			if(memo.containsKey(A[i]-1)){
  				tot2+=(int)memo.get(A[i]-1);
  			}
  			if(memo.containsKey(A[i]+1)){
  				tot2+=(int)memo.get(A[i]+1);
  			}
  			tot2+=(int)memo.get(A[i]);
  			tot2=n-i-1-(tot2-f[i]);
  			//res+=(long)(tot1-tot2)*(long)A[i];
  			res=res.add(BigInteger.valueOf((long)(tot1-tot2)*(long)A[i]));
  		}
  		System.out.println(res);
  	}
  }