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

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];
		for (int i=0;i<N;i++) {
			A[i] = sc.nextInt();
		}
		Arrays.parallelSort(A);
		int sum =0;
		for (int i=N-1;i>=0;i-=2) {
			if (i==0) {
				sum +=A[0];
			} else {
				sum +=A[i]-A[i-1];
			}
		}
		System.out.println(sum);
	}
} import java.util.Arrays; Arrays 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();
		int A[] = new int[N];
		for (int i=0;i<N;i++) {
			A[i] = sc.nextInt();
		}
		Arrays.parallelSort(A);
		int sum =0;
		for (int i=N-1;i>=0;i-=2) {
			if (i==0) {
				sum +=A[0];
			} else {
				sum +=A[i]-A[i-1];
			}
		}
		System.out.println(sum);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];
		for (int i=0;i<N;i++) {
			A[i] = sc.nextInt();
		}
		Arrays.parallelSort(A);
		int sum =0;
		for (int i=N-1;i>=0;i-=2) {
			if (i==0) {
				sum +=A[0];
			} else {
				sum +=A[i]-A[i-1];
			}
		}
		System.out.println(sum);
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];
		for (int i=0;i<N;i++) {
			A[i] = sc.nextInt();
		}
		Arrays.parallelSort(A);
		int sum =0;
		for (int i=N-1;i>=0;i-=2) {
			if (i==0) {
				sum +=A[0];
			} else {
				sum +=A[i]-A[i-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 int A[] = new int[N]; A new int[N] N for (int i=0;i<N;i++) {
			A[i] = sc.nextInt();
		} int i=0; int 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.parallelSort(A) Arrays.parallelSort Arrays A int sum =0; sum 0 for (int i=N-1;i>=0;i-=2) {
			if (i==0) {
				sum +=A[0];
			} else {
				sum +=A[i]-A[i-1];
			}
		} int i=N-1; int i=N-1; i N-1 N 1 i>=0 i 0 i-=2 i-=2 i 2 {
			if (i==0) {
				sum +=A[0];
			} else {
				sum +=A[i]-A[i-1];
			}
		} {
			if (i==0) {
				sum +=A[0];
			} else {
				sum +=A[i]-A[i-1];
			}
		} if (i==0) {
				sum +=A[0];
			} else {
				sum +=A[i]-A[i-1];
			} i==0 i 0 {
				sum +=A[0];
			} sum +=A[0] sum A[0] A 0 {
				sum +=A[i]-A[i-1];
			} sum +=A[i]-A[i-1] sum A[i]-A[i-1] A[i] A i A[i-1] A i-1 i 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();
		int A[] = new int[N];
		for (int i=0;i<N;i++) {
			A[i] = sc.nextInt();
		}
		Arrays.parallelSort(A);
		int sum =0;
		for (int i=N-1;i>=0;i-=2) {
			if (i==0) {
				sum +=A[0];
			} else {
				sum +=A[i]-A[i-1];
			}
		}
		System.out.println(sum);
	}
} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];
		for (int i=0;i<N;i++) {
			A[i] = sc.nextInt();
		}
		Arrays.parallelSort(A);
		int sum =0;
		for (int i=N-1;i>=0;i-=2) {
			if (i==0) {
				sum +=A[0];
			} else {
				sum +=A[i]-A[i-1];
			}
		}
		System.out.println(sum);
	}
} Main
import java.util.Arrays;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int A[] = new int[N];
		for (int i=0;i<N;i++) {
			A[i] = sc.nextInt();
		}
		Arrays.parallelSort(A);
		int sum =0;
		for (int i=N-1;i>=0;i-=2) {
			if (i==0) {
				sum +=A[0];
			} else {
				sum +=A[i]-A[i-1];
			}
		}
		System.out.println(sum);
	}
}