
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;

public class Main {
	private static final int MOD = (int)Math.pow(10, 9);
	public static void main(String[] args) {
		FastReader sc = new FastReader();
		int n = sc.nextInt();
		int[] cards = new int[n];
		for (int i = 0; i < n; i++) { cards[i] = sc.nextInt();}
		Arrays.sort(cards);
		
		int pos = n - 1;
		int alice = 0;
		while (pos >= 0) {
			alice += cards[pos];
			pos -= 2;
		}
		
		pos = n - 2;
		int bob = 0;
		while (pos >= 0) {
			bob += cards[pos];
			pos -= 2;
		}
		
		System.out.println(alice - bob);
	}
	
	static class FastReader {
	    BufferedReader br;
	    StringTokenizer st;
	
	    public FastReader() {
	      br = new BufferedReader(new InputStreamReader(System.in));
	    }
	  
	    String next() { 
	      while (st == null || !st.hasMoreElements()) {
	        try {
	          st = new StringTokenizer(br.readLine());
	        } catch (IOException  e) {
	          e.printStackTrace();
	        }
	      }
	      return st.nextToken();
	    }
	
	    int nextInt() {
	      return Integer.parseInt(next());
	    }
	
	    long nextLong() {
	      return Long.parseLong(next());
	    }
	
	    double nextDouble() { 
	      return Double.parseDouble(next());
	    }
	
	    String nextLine() {
	      String str = "";
	        try{
	            str = br.readLine();
	        } catch (IOException e) {
	            e.printStackTrace();
	        }
	        return str;
	      }
	  }
} import java.io.BufferedReader; BufferedReader java.io import java.io.IOException; IOException java.io import java.io.InputStreamReader; InputStreamReader java.io import java.util.Arrays; Arrays java.util import java.util.StringTokenizer; StringTokenizer java.util public class Main {
	private static final int MOD = (int)Math.pow(10, 9);
	public static void main(String[] args) {
		FastReader sc = new FastReader();
		int n = sc.nextInt();
		int[] cards = new int[n];
		for (int i = 0; i < n; i++) { cards[i] = sc.nextInt();}
		Arrays.sort(cards);
		
		int pos = n - 1;
		int alice = 0;
		while (pos >= 0) {
			alice += cards[pos];
			pos -= 2;
		}
		
		pos = n - 2;
		int bob = 0;
		while (pos >= 0) {
			bob += cards[pos];
			pos -= 2;
		}
		
		System.out.println(alice - bob);
	}
	
	static class FastReader {
	    BufferedReader br;
	    StringTokenizer st;
	
	    public FastReader() {
	      br = new BufferedReader(new InputStreamReader(System.in));
	    }
	  
	    String next() { 
	      while (st == null || !st.hasMoreElements()) {
	        try {
	          st = new StringTokenizer(br.readLine());
	        } catch (IOException  e) {
	          e.printStackTrace();
	        }
	      }
	      return st.nextToken();
	    }
	
	    int nextInt() {
	      return Integer.parseInt(next());
	    }
	
	    long nextLong() {
	      return Long.parseLong(next());
	    }
	
	    double nextDouble() { 
	      return Double.parseDouble(next());
	    }
	
	    String nextLine() {
	      String str = "";
	        try{
	            str = br.readLine();
	        } catch (IOException e) {
	            e.printStackTrace();
	        }
	        return str;
	      }
	  }
} Main private static final int MOD = (int)Math.pow(10, 9); MOD (int)Math.pow(10, 9) Math.pow Math 10 9 public static void main(String[] args) {
		FastReader sc = new FastReader();
		int n = sc.nextInt();
		int[] cards = new int[n];
		for (int i = 0; i < n; i++) { cards[i] = sc.nextInt();}
		Arrays.sort(cards);
		
		int pos = n - 1;
		int alice = 0;
		while (pos >= 0) {
			alice += cards[pos];
			pos -= 2;
		}
		
		pos = n - 2;
		int bob = 0;
		while (pos >= 0) {
			bob += cards[pos];
			pos -= 2;
		}
		
		System.out.println(alice - bob);
	} main {
		FastReader sc = new FastReader();
		int n = sc.nextInt();
		int[] cards = new int[n];
		for (int i = 0; i < n; i++) { cards[i] = sc.nextInt();}
		Arrays.sort(cards);
		
		int pos = n - 1;
		int alice = 0;
		while (pos >= 0) {
			alice += cards[pos];
			pos -= 2;
		}
		
		pos = n - 2;
		int bob = 0;
		while (pos >= 0) {
			bob += cards[pos];
			pos -= 2;
		}
		
		System.out.println(alice - bob);
	} FastReader sc = new FastReader(); sc new FastReader() int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int[] cards = new int[n]; cards new int[n] n for (int i = 0; i < n; i++) { cards[i] = sc.nextInt();} int i = 0; int i = 0; i 0 i < n i n i++ i++ i { cards[i] = sc.nextInt();} { cards[i] = sc.nextInt();} cards[i] = sc.nextInt() cards[i] cards i sc.nextInt() sc.nextInt sc Arrays.sort(cards) Arrays.sort Arrays cards int pos = n - 1; pos n - 1 n 1 int alice = 0; alice 0 while (pos >= 0) {
			alice += cards[pos];
			pos -= 2;
		} pos >= 0 pos 0 {
			alice += cards[pos];
			pos -= 2;
		} alice += cards[pos] alice cards[pos] cards pos pos -= 2 pos 2 pos = n - 2 pos n - 2 n 2 int bob = 0; bob 0 while (pos >= 0) {
			bob += cards[pos];
			pos -= 2;
		} pos >= 0 pos 0 {
			bob += cards[pos];
			pos -= 2;
		} bob += cards[pos] bob cards[pos] cards pos pos -= 2 pos 2 System.out.println(alice - bob) System.out.println System.out System System.out alice - bob alice bob String[] args args static class FastReader {
	    BufferedReader br;
	    StringTokenizer st;
	
	    public FastReader() {
	      br = new BufferedReader(new InputStreamReader(System.in));
	    }
	  
	    String next() { 
	      while (st == null || !st.hasMoreElements()) {
	        try {
	          st = new StringTokenizer(br.readLine());
	        } catch (IOException  e) {
	          e.printStackTrace();
	        }
	      }
	      return st.nextToken();
	    }
	
	    int nextInt() {
	      return Integer.parseInt(next());
	    }
	
	    long nextLong() {
	      return Long.parseLong(next());
	    }
	
	    double nextDouble() { 
	      return Double.parseDouble(next());
	    }
	
	    String nextLine() {
	      String str = "";
	        try{
	            str = br.readLine();
	        } catch (IOException e) {
	            e.printStackTrace();
	        }
	        return str;
	      }
	  } FastReader BufferedReader br; br StringTokenizer st; st public FastReader() {
	      br = new BufferedReader(new InputStreamReader(System.in));
	    } FastReader {
	      br = new BufferedReader(new InputStreamReader(System.in));
	    } br = new BufferedReader(new InputStreamReader(System.in)) br new BufferedReader(new InputStreamReader(System.in)) String next() { 
	      while (st == null || !st.hasMoreElements()) {
	        try {
	          st = new StringTokenizer(br.readLine());
	        } catch (IOException  e) {
	          e.printStackTrace();
	        }
	      }
	      return st.nextToken();
	    } next { 
	      while (st == null || !st.hasMoreElements()) {
	        try {
	          st = new StringTokenizer(br.readLine());
	        } catch (IOException  e) {
	          e.printStackTrace();
	        }
	      }
	      return st.nextToken();
	    } while (st == null || !st.hasMoreElements()) {
	        try {
	          st = new StringTokenizer(br.readLine());
	        } catch (IOException  e) {
	          e.printStackTrace();
	        }
	      } st == null || !st.hasMoreElements() st == null st null !st.hasMoreElements() st.hasMoreElements() st.hasMoreElements st {
	        try {
	          st = new StringTokenizer(br.readLine());
	        } catch (IOException  e) {
	          e.printStackTrace();
	        }
	      } try {
	          st = new StringTokenizer(br.readLine());
	        } catch (IOException  e) {
	          e.printStackTrace();
	        } catch (IOException  e) {
	          e.printStackTrace();
	        } IOException  e {
	          e.printStackTrace();
	        } e.printStackTrace() e.printStackTrace e {
	          st = new StringTokenizer(br.readLine());
	        } st = new StringTokenizer(br.readLine()) st new StringTokenizer(br.readLine()) return st.nextToken(); st.nextToken() st.nextToken st int nextInt() {
	      return Integer.parseInt(next());
	    } nextInt {
	      return Integer.parseInt(next());
	    } return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next long nextLong() {
	      return Long.parseLong(next());
	    } nextLong {
	      return Long.parseLong(next());
	    } return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next double nextDouble() { 
	      return Double.parseDouble(next());
	    } nextDouble { 
	      return Double.parseDouble(next());
	    } return Double.parseDouble(next()); Double.parseDouble(next()) Double.parseDouble Double next() next String nextLine() {
	      String str = "";
	        try{
	            str = br.readLine();
	        } catch (IOException e) {
	            e.printStackTrace();
	        }
	        return str;
	      } nextLine {
	      String str = "";
	        try{
	            str = br.readLine();
	        } catch (IOException e) {
	            e.printStackTrace();
	        }
	        return str;
	      } String str = ""; str "" try{
	            str = br.readLine();
	        } catch (IOException e) {
	            e.printStackTrace();
	        } catch (IOException e) {
	            e.printStackTrace();
	        } IOException e {
	            e.printStackTrace();
	        } e.printStackTrace() e.printStackTrace e {
	            str = br.readLine();
	        } str = br.readLine() str br.readLine() br.readLine br return str; str public class Main {
	private static final int MOD = (int)Math.pow(10, 9);
	public static void main(String[] args) {
		FastReader sc = new FastReader();
		int n = sc.nextInt();
		int[] cards = new int[n];
		for (int i = 0; i < n; i++) { cards[i] = sc.nextInt();}
		Arrays.sort(cards);
		
		int pos = n - 1;
		int alice = 0;
		while (pos >= 0) {
			alice += cards[pos];
			pos -= 2;
		}
		
		pos = n - 2;
		int bob = 0;
		while (pos >= 0) {
			bob += cards[pos];
			pos -= 2;
		}
		
		System.out.println(alice - bob);
	}
	
	static class FastReader {
	    BufferedReader br;
	    StringTokenizer st;
	
	    public FastReader() {
	      br = new BufferedReader(new InputStreamReader(System.in));
	    }
	  
	    String next() { 
	      while (st == null || !st.hasMoreElements()) {
	        try {
	          st = new StringTokenizer(br.readLine());
	        } catch (IOException  e) {
	          e.printStackTrace();
	        }
	      }
	      return st.nextToken();
	    }
	
	    int nextInt() {
	      return Integer.parseInt(next());
	    }
	
	    long nextLong() {
	      return Long.parseLong(next());
	    }
	
	    double nextDouble() { 
	      return Double.parseDouble(next());
	    }
	
	    String nextLine() {
	      String str = "";
	        try{
	            str = br.readLine();
	        } catch (IOException e) {
	            e.printStackTrace();
	        }
	        return str;
	      }
	  }
} public class Main {
	private static final int MOD = (int)Math.pow(10, 9);
	public static void main(String[] args) {
		FastReader sc = new FastReader();
		int n = sc.nextInt();
		int[] cards = new int[n];
		for (int i = 0; i < n; i++) { cards[i] = sc.nextInt();}
		Arrays.sort(cards);
		
		int pos = n - 1;
		int alice = 0;
		while (pos >= 0) {
			alice += cards[pos];
			pos -= 2;
		}
		
		pos = n - 2;
		int bob = 0;
		while (pos >= 0) {
			bob += cards[pos];
			pos -= 2;
		}
		
		System.out.println(alice - bob);
	}
	
	static class FastReader {
	    BufferedReader br;
	    StringTokenizer st;
	
	    public FastReader() {
	      br = new BufferedReader(new InputStreamReader(System.in));
	    }
	  
	    String next() { 
	      while (st == null || !st.hasMoreElements()) {
	        try {
	          st = new StringTokenizer(br.readLine());
	        } catch (IOException  e) {
	          e.printStackTrace();
	        }
	      }
	      return st.nextToken();
	    }
	
	    int nextInt() {
	      return Integer.parseInt(next());
	    }
	
	    long nextLong() {
	      return Long.parseLong(next());
	    }
	
	    double nextDouble() { 
	      return Double.parseDouble(next());
	    }
	
	    String nextLine() {
	      String str = "";
	        try{
	            str = br.readLine();
	        } catch (IOException e) {
	            e.printStackTrace();
	        }
	        return str;
	      }
	  }
} Main

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;

public class Main {
	private static final int MOD = (int)Math.pow(10, 9);
	public static void main(String[] args) {
		FastReader sc = new FastReader();
		int n = sc.nextInt();
		int[] cards = new int[n];
		for (int i = 0; i < n; i++) { cards[i] = sc.nextInt();}
		Arrays.sort(cards);
		
		int pos = n - 1;
		int alice = 0;
		while (pos >= 0) {
			alice += cards[pos];
			pos -= 2;
		}
		
		pos = n - 2;
		int bob = 0;
		while (pos >= 0) {
			bob += cards[pos];
			pos -= 2;
		}
		
		System.out.println(alice - bob);
	}
	
	static class FastReader {
	    BufferedReader br;
	    StringTokenizer st;
	
	    public FastReader() {
	      br = new BufferedReader(new InputStreamReader(System.in));
	    }
	  
	    String next() { 
	      while (st == null || !st.hasMoreElements()) {
	        try {
	          st = new StringTokenizer(br.readLine());
	        } catch (IOException  e) {
	          e.printStackTrace();
	        }
	      }
	      return st.nextToken();
	    }
	
	    int nextInt() {
	      return Integer.parseInt(next());
	    }
	
	    long nextLong() {
	      return Long.parseLong(next());
	    }
	
	    double nextDouble() { 
	      return Double.parseDouble(next());
	    }
	
	    String nextLine() {
	      String str = "";
	        try{
	            str = br.readLine();
	        } catch (IOException e) {
	            e.printStackTrace();
	        }
	        return str;
	      }
	  }
}
