import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;


public class Main {

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int N=sc.nextInt();
		Integer a[]=new Integer[N];
		int i;
		int sum=0;
		for(i=0;i<N;++i) {
			a[i]=sc.nextInt();
		}
		Arrays.sort(a,Comparator.reverseOrder());
		if(N%2==0) {
			for(i=0;i<N/2;++i) {
				sum+=(a[2*i]-a[2*i+1]);
			}}
		if(N%2==1) {
			for(i=0;i<N/2;++i) {
			sum+=(a[2*i]-a[2*i+1]);}
			sum+=a[N-1];
		}
			
			System.out.println(sum);
			
		
	}

} import java.util.Arrays; Arrays java.util import java.util.Comparator; Comparator java.util import java.util.Scanner; Scanner java.util public class Main {

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int N=sc.nextInt();
		Integer a[]=new Integer[N];
		int i;
		int sum=0;
		for(i=0;i<N;++i) {
			a[i]=sc.nextInt();
		}
		Arrays.sort(a,Comparator.reverseOrder());
		if(N%2==0) {
			for(i=0;i<N/2;++i) {
				sum+=(a[2*i]-a[2*i+1]);
			}}
		if(N%2==1) {
			for(i=0;i<N/2;++i) {
			sum+=(a[2*i]-a[2*i+1]);}
			sum+=a[N-1];
		}
			
			System.out.println(sum);
			
		
	}

} Main public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int N=sc.nextInt();
		Integer a[]=new Integer[N];
		int i;
		int sum=0;
		for(i=0;i<N;++i) {
			a[i]=sc.nextInt();
		}
		Arrays.sort(a,Comparator.reverseOrder());
		if(N%2==0) {
			for(i=0;i<N/2;++i) {
				sum+=(a[2*i]-a[2*i+1]);
			}}
		if(N%2==1) {
			for(i=0;i<N/2;++i) {
			sum+=(a[2*i]-a[2*i+1]);}
			sum+=a[N-1];
		}
			
			System.out.println(sum);
			
		
	} main {
		Scanner sc=new Scanner(System.in);
		int N=sc.nextInt();
		Integer a[]=new Integer[N];
		int i;
		int sum=0;
		for(i=0;i<N;++i) {
			a[i]=sc.nextInt();
		}
		Arrays.sort(a,Comparator.reverseOrder());
		if(N%2==0) {
			for(i=0;i<N/2;++i) {
				sum+=(a[2*i]-a[2*i+1]);
			}}
		if(N%2==1) {
			for(i=0;i<N/2;++i) {
			sum+=(a[2*i]-a[2*i+1]);}
			sum+=a[N-1];
		}
			
			System.out.println(sum);
			
		
	} Scanner sc=new Scanner(System.in); sc new Scanner(System.in) int N=sc.nextInt(); N sc.nextInt() sc.nextInt sc Integer a[]=new Integer[N]; a new Integer[N] N int i; i int sum=0; sum 0 for(i=0;i<N;++i) {
			a[i]=sc.nextInt();
		} i=0; i=0 i 0 i<N i N ++i ++i i {
			a[i]=sc.nextInt();
		} {
			a[i]=sc.nextInt();
		} a[i]=sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc Arrays.sort(a,Comparator.reverseOrder()) Arrays.sort Arrays a Comparator.reverseOrder() Comparator.reverseOrder Comparator if(N%2==0) {
			for(i=0;i<N/2;++i) {
				sum+=(a[2*i]-a[2*i+1]);
			}} N%2==0 N%2 N 2 0 {
			for(i=0;i<N/2;++i) {
				sum+=(a[2*i]-a[2*i+1]);
			}} for(i=0;i<N/2;++i) {
				sum+=(a[2*i]-a[2*i+1]);
			} i=0; i=0 i 0 i<N/2 i N/2 N 2 ++i ++i i {
				sum+=(a[2*i]-a[2*i+1]);
			} {
				sum+=(a[2*i]-a[2*i+1]);
			} sum+=(a[2*i]-a[2*i+1]) sum (a[2*i]-a[2*i+1]) a[2*i] a 2*i 2 i a[2*i+1] a 2*i+1 2*i 2 i 1 if(N%2==1) {
			for(i=0;i<N/2;++i) {
			sum+=(a[2*i]-a[2*i+1]);}
			sum+=a[N-1];
		} N%2==1 N%2 N 2 1 {
			for(i=0;i<N/2;++i) {
			sum+=(a[2*i]-a[2*i+1]);}
			sum+=a[N-1];
		} for(i=0;i<N/2;++i) {
			sum+=(a[2*i]-a[2*i+1]);} i=0; i=0 i 0 i<N/2 i N/2 N 2 ++i ++i i {
			sum+=(a[2*i]-a[2*i+1]);} {
			sum+=(a[2*i]-a[2*i+1]);} sum+=(a[2*i]-a[2*i+1]) sum (a[2*i]-a[2*i+1]) a[2*i] a 2*i 2 i a[2*i+1] a 2*i+1 2*i 2 i 1 sum+=a[N-1] sum a[N-1] a N-1 N 1 System.out.println(sum) System.out.println System.out System System.out sum String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int N=sc.nextInt();
		Integer a[]=new Integer[N];
		int i;
		int sum=0;
		for(i=0;i<N;++i) {
			a[i]=sc.nextInt();
		}
		Arrays.sort(a,Comparator.reverseOrder());
		if(N%2==0) {
			for(i=0;i<N/2;++i) {
				sum+=(a[2*i]-a[2*i+1]);
			}}
		if(N%2==1) {
			for(i=0;i<N/2;++i) {
			sum+=(a[2*i]-a[2*i+1]);}
			sum+=a[N-1];
		}
			
			System.out.println(sum);
			
		
	}

} public class Main {

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int N=sc.nextInt();
		Integer a[]=new Integer[N];
		int i;
		int sum=0;
		for(i=0;i<N;++i) {
			a[i]=sc.nextInt();
		}
		Arrays.sort(a,Comparator.reverseOrder());
		if(N%2==0) {
			for(i=0;i<N/2;++i) {
				sum+=(a[2*i]-a[2*i+1]);
			}}
		if(N%2==1) {
			for(i=0;i<N/2;++i) {
			sum+=(a[2*i]-a[2*i+1]);}
			sum+=a[N-1];
		}
			
			System.out.println(sum);
			
		
	}

} Main
import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;


public class Main {

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int N=sc.nextInt();
		Integer a[]=new Integer[N];
		int i;
		int sum=0;
		for(i=0;i<N;++i) {
			a[i]=sc.nextInt();
		}
		Arrays.sort(a,Comparator.reverseOrder());
		if(N%2==0) {
			for(i=0;i<N/2;++i) {
				sum+=(a[2*i]-a[2*i+1]);
			}}
		if(N%2==1) {
			for(i=0;i<N/2;++i) {
			sum+=(a[2*i]-a[2*i+1]);}
			sum+=a[N-1];
		}
			
			System.out.println(sum);
			
		
	}

}
