// Problem: 903_D. Almost Difference
// Time complexity: nlogn
import java.io.*;
     
     
     
     
    import java.math.*;
    import java.util.*;    
          public class Main1
           {
            private InputStream is;
            private PrintWriter out;
            static int MOD = (int)(1e9+7);
            ArrayList<Integer>[] amp;
            public static void main(String[] args) throws Exception
            {
                new Thread(null, new Runnable()
                {
                public void run()
                {
                    try {
         } catch (Exception e)
                    {
                        System.out.println(e);
                    }
                }
            }, "1", 1 << 26).start();
                new Main1().soln();
            }
            char ch[][];
            static ArrayList<Integer>[] g;
            static ArrayList<Integer> ar[];
            static long ok[];    
            static int phi[]=new int[500005];
            void solve()
            {
            	int n=ni();
                int a[]=na(n);
                long sum=0;
                HashMap<Integer,Integer> hm=new HashMap();
                BigInteger ans=(BigInteger.ZERO);
                int count=0;
                for(int i=n-1;i>=0;i--)
                {
               	 int tmp1=0;
               	 int tmp2=0;
               	 int tmp3=0;
               	 if(hm.containsKey(a[i]))
               		 tmp1=hm.get(a[i]);
               	 if(hm.containsKey(a[i]+1))
               		 tmp2=hm.get(a[i]+1);
               	 if(hm.containsKey(a[i]-1))
               		 tmp3=hm.get(a[i]-1);
               	 long lol=sum;
               	 lol-=((long)tmp1*(long)a[i]);
               	 lol-=((long)tmp2*(long)(a[i]+1));
               	 lol-=((long)tmp3*(long)(a[i]-1));
               	 int fr=(count)-tmp1-tmp2-tmp3;
               	 long fuck=(lol)-((long)fr*(long)a[i]);
               	 ans=ans.add(BigInteger.valueOf(fuck));
               	 if(!hm.containsKey(a[i]))
               		 hm.put(a[i],1);
               	 else
               		 hm.put(a[i],hm.get(a[i])+1);
               	 sum+=(long)a[i];
               	 count++;
               	// System.out.println(ans+" "+tmp1+" "+tmp2+" "+tmp3+" "+lol);
                }
                out.println(ans);
            }
           public static long multiply(long a)
            {
            	return a*10;
            }
            public static long query1(int v,int start,int end,int l,int r,int x)
            {
            	if(r < start || end < l)
                {
                    return Long.MAX_VALUE;
                }
                if(l <= start && end <= r)
                {
                    return (tre[v]);
                }
                int mid = (start + end) / 2;
                long p1 = query1(2*v, start, mid, l, r,x);
                long p2 = query1(2*v+1, mid+1, end, l, r,x);
                return Math.min(p1, p2);	
            }
            public static void update1(int v,int tl,int tr,int index,long a2)
            {
            	if(tl==tr)
                {
                    tre[v]=a2;
                }
                else
                {
                    int mid=(tl+tr)/2;
                    if(tl <= index &&index <= mid)
                    {
                        update1(2*v,tl, mid, index, a2);
                    }
                    else
                    {
                        update1(2*v+1,mid+1,tr, index, a2);
                    }
                    tre[v]=(Math.min(tre[2*v],tre[2*v+1]));
                }
            }
			static boolean visited[][];
			static int a[][];
            public static long query(int v,int start,int end,int l,int r,int x)
            {
            	if(r < start || end < l)
                {
                    return 0;
                }
                if(l <= start && end <= r)
                {
                    return (tre[v]);
                }
                int mid = (start + end) / 2;
                long p1 = query(2*v, start, mid, l, r,x);
                long p2 = query(2*v+1, mid+1, end, l, r,x);
                return Math.max(p1, p2);	
            }
            public static void update(int v,int tl,int tr,int index,long a2)
            {
            	if(tl==tr)
                {
                    tre[v]=a2;
                }
                else
                {
                    int mid=(tl+tr)/2;
                    if(tl <= index &&index <= mid)
                    {
                        update(2*v,tl, mid, index, a2);
                    }
                    else
                    {
                        update(2*v+1,mid+1,tr, index, a2);
                    }
                    tre[v]=(Math.max(tre[2*v],tre[2*v+1]));
                }
            }
            static long tre[]=new long[400005];
          /* public static int find(int v,int start,int end,int l,int r)
            {
                if(r < start || end < l)
                {
                    return Integer.MIN_VALUE;
                }
                if(l <= start && end <= r)
                {
                    return (tre[v]);
                }
                int mid = (start + end) / 2;
                int p1 = find(2*v, start, mid, l, r);
                int p2 = find(2*v+1, mid+1, end, l, r);
                return Math.max(p1, p2);          
            }
            static int tre[]=new int[4000005];
            public static void Update(int v,int tl,int tr,int index,int val)
            {
                if(tl==tr)
                {
                    tre[v]=val;
                }
                else
                {
                    int mid=(tl+tr)/2;
                    if(tl <= index &&index <= mid)
                    {
                        Update(2*v,tl, mid, index, val);
                    }
                    else
                    {
                        Update(2*v+1,mid+1,tr, index, val);
                    }
                    tre[v]=(Math.max(tre[2*v],tre[2*v+1]));
                }
            }
            */
            boolean isPrime(int x)
                {
                if(x==0||x==1)
                    return false;
                for(int i = 2;i*1L*i<=x;i++) if(x%i==0) return false;
                return true;
            }
            int  p ;
            long modInverse(long a, long mOD2){
                return  power(a, mOD2-2, mOD2);
            }
            long power(long x, long y, long m)
            {
            if (y == 0)
            return 1;
            long p = power(x, y/2, m) % m;
            p = (p * p) % m;
        
            return (y%2 == 0)? p : (x * p) % m;
            }
            public static long gcd(long a, long b){
                if(b==0) return a;
                return gcd(b,a%b);
            }
            class Pair1 implements Comparable<Pair1>{
                long a;
                long b;
                long c;
                Pair1(long x,long y,long z){
                this.a=x;
                this.b=y;
                this.c=z;
                }
                public int hashCode() {
                    return Objects.hash();
                }
                
                @Override
                public int compareTo(Pair1 arg0) {
                    return (int)(arg0.c-c);
                }    
            }
            long power(long x, long y, int mod){
                long ans = 1;
                while(y>0){
                    if(y%2==0){
                        x = (x*x)%mod;
                        y/=2;
                    }
                    else{
                        ans = (x*ans)%mod;
                        y--;
                    }
                }
                return ans;
            }
            void soln() {
                is = System.in;
                out = new PrintWriter(System.out);
                long s = System.currentTimeMillis();
                solve();
                out.flush();
            }
             private byte[] inbuf = new byte[1024];
            public int lenbuf = 0, ptrbuf = 0;
            private int readByte() {
                if (lenbuf == -1)
                    throw new InputMismatchException();
                if (ptrbuf >= lenbuf) {
                    ptrbuf = 0;
                    try {
                        lenbuf = is.read(inbuf);
                    } catch (IOException e) {
                        throw new InputMismatchException();
                    }
                    if (lenbuf <= 0)
                        return -1;
                }
                return inbuf[ptrbuf++];
            }
            private boolean isSpaceChar(int c) {
                return !(c >= 33 && c <= 126);
            }
            private int skip() {
                int b;
                while ((b = readByte()) != -1 && isSpaceChar(b))
                    ;
                return b;
            }
            private double nd() {
                return Double.parseDouble(ns());
            }
            private char nc() {
                return (char) skip();
            }
            private String ns() {
                int b = skip();
                StringBuilder sb = new StringBuilder();
                while (!(isSpaceChar(b))) {
                    sb.appendCodePoint(b);
                    b = readByte();
                }
                return sb.toString();
            }
            private char[] ns(int n) {
                char[] buf = new char[n];
                int b = skip(), p = 0;
                while (p < n && !(isSpaceChar(b))) {
                    buf[p++] = (char) b;
                    b = readByte();
                }
                return n == p ? buf : Arrays.copyOf(buf, p);
            }
            private int[][] nm(int n, int m) {
                int[][] map = new int[n][m];
                for (int i = 0; i < n; i++)
                {
                    for(int j=0;j<m;j++)
                        map[i][j]=ni();
                }
                return map;
            }
            private int[] na(int n) {
                int[] a = new int[n];
                for (int i = 0; i < n; i++)
                    a[i] = ni();
                return a;
            }
            private int ni() {
                int num = 0, b;
                boolean minus = false;
                while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
                    ;
                if (b == '-') {
                    minus = true;
                    b = readByte();
                }
                while (true) {
                    if (b >= '0' && b <= '9') {
                        num = num * 10 + (b - '0');
                    } else {
                        return minus ? -num : num;
                    }
                    b = readByte();
                }
            }
            private long nl() {
                long num = 0;
                int b;
                boolean minus = false;
                while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
                    ;
                if (b == '-') {
                    minus = true;
                    b = readByte();
                }
                while (true) {
                    if (b >= '0' && b <= '9') {
                        num = num * 10 + (b - '0');
                    } else {
                        return minus ? -num : num;
                    }
                    b = readByte();
                }
            }
            private boolean oj = System.getProperty("ONLINE_JUDGE") != null;
            private void tr(Object... o) {
                if (!oj)
                    System.out.println(Arrays.deepToString(o));
            }
        }