import java.io.PrintStream;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	static final PrintStream out = System.out;
	static Scanner sc = new Scanner(System.in);
	static final long Mod = 1000_000_007L;
	public static void main(String[] args) {
		Main main = new Main();
		main.solve();
		System.exit(0);
	}

	void solve() {
		int N = nextInt();
		int[] A = nextIntArray(N);

		Arrays.sort(A);

		int cnt = 0;
		if(N % 2 == 1) {
			out.println(0);
			return;
		}

		int L = A[N/2-1];
		int R = A[N/2];

		cnt = R - L;

		//out.println(Arrays.toString(A));
		out.println(cnt);
	}

	public int[] nextIntArray(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)a[i] = nextInt();
		return a;
	}
	public long[] nextLongArray(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)a[i] = nextLong();
		return a;
	}
	public int nextInt() {
		return Integer.parseInt(next());
	}
	public long nextLong() {
		return Long.parseLong(next());
	}
	public String next() {
		return sc.next();
	}

} import java.io.PrintStream; PrintStream java.io import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {
	static final PrintStream out = System.out;
	static Scanner sc = new Scanner(System.in);
	static final long Mod = 1000_000_007L;
	public static void main(String[] args) {
		Main main = new Main();
		main.solve();
		System.exit(0);
	}

	void solve() {
		int N = nextInt();
		int[] A = nextIntArray(N);

		Arrays.sort(A);

		int cnt = 0;
		if(N % 2 == 1) {
			out.println(0);
			return;
		}

		int L = A[N/2-1];
		int R = A[N/2];

		cnt = R - L;

		//out.println(Arrays.toString(A));
		out.println(cnt);
	}

	public int[] nextIntArray(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)a[i] = nextInt();
		return a;
	}
	public long[] nextLongArray(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)a[i] = nextLong();
		return a;
	}
	public int nextInt() {
		return Integer.parseInt(next());
	}
	public long nextLong() {
		return Long.parseLong(next());
	}
	public String next() {
		return sc.next();
	}

} Main static final PrintStream out = System.out; out System.out System System.out static Scanner sc = new Scanner(System.in); sc new Scanner(System.in) static final long Mod = 1000_000_007L; Mod 1000_000_007L public static void main(String[] args) {
		Main main = new Main();
		main.solve();
		System.exit(0);
	} main {
		Main main = new Main();
		main.solve();
		System.exit(0);
	} Main main = new Main(); main new Main() main.solve() main.solve main System.exit(0) System.exit System 0 String[] args args void solve() {
		int N = nextInt();
		int[] A = nextIntArray(N);

		Arrays.sort(A);

		int cnt = 0;
		if(N % 2 == 1) {
			out.println(0);
			return;
		}

		int L = A[N/2-1];
		int R = A[N/2];

		cnt = R - L;

		//out.println(Arrays.toString(A));
		out.println(cnt);
	} solve {
		int N = nextInt();
		int[] A = nextIntArray(N);

		Arrays.sort(A);

		int cnt = 0;
		if(N % 2 == 1) {
			out.println(0);
			return;
		}

		int L = A[N/2-1];
		int R = A[N/2];

		cnt = R - L;

		//out.println(Arrays.toString(A));
		out.println(cnt);
	} int N = nextInt(); N nextInt() nextInt int[] A = nextIntArray(N); A nextIntArray(N) nextIntArray N Arrays.sort(A) Arrays.sort Arrays A int cnt = 0; cnt 0 if(N % 2 == 1) {
			out.println(0);
			return;
		} N % 2 == 1 N % 2 N 2 1 {
			out.println(0);
			return;
		} out.println(0) out.println out 0 return; int L = A[N/2-1]; L A[N/2-1] A N/2-1 N/2 N 2 1 int R = A[N/2]; R A[N/2] A N/2 N 2 cnt = R - L cnt R - L R L out.println(cnt) out.println out cnt public int[] nextIntArray(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)a[i] = nextInt();
		return a;
	} nextIntArray {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)a[i] = nextInt();
		return a;
	} int[] a = new int[n]; a new int[n] n for (int i = 0; i < n; i++)a[i] = nextInt(); int i = 0; int i = 0; i 0 i < n i n i++ i++ i a[i] = nextInt(); a[i] = nextInt() a[i] a i nextInt() nextInt return a; a int n n public long[] nextLongArray(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)a[i] = nextLong();
		return a;
	} nextLongArray {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)a[i] = nextLong();
		return a;
	} long[] a = new long[n]; a new long[n] n for (int i = 0; i < n; i++)a[i] = nextLong(); int i = 0; int i = 0; i 0 i < n i n i++ i++ i a[i] = nextLong(); a[i] = nextLong() a[i] a i nextLong() nextLong return a; a int n n public int nextInt() {
		return Integer.parseInt(next());
	} nextInt {
		return Integer.parseInt(next());
	} return Integer.parseInt(next()); Integer.parseInt(next()) Integer.parseInt Integer next() next public long nextLong() {
		return Long.parseLong(next());
	} nextLong {
		return Long.parseLong(next());
	} return Long.parseLong(next()); Long.parseLong(next()) Long.parseLong Long next() next public String next() {
		return sc.next();
	} next {
		return sc.next();
	} return sc.next(); sc.next() sc.next sc public class Main {
	static final PrintStream out = System.out;
	static Scanner sc = new Scanner(System.in);
	static final long Mod = 1000_000_007L;
	public static void main(String[] args) {
		Main main = new Main();
		main.solve();
		System.exit(0);
	}

	void solve() {
		int N = nextInt();
		int[] A = nextIntArray(N);

		Arrays.sort(A);

		int cnt = 0;
		if(N % 2 == 1) {
			out.println(0);
			return;
		}

		int L = A[N/2-1];
		int R = A[N/2];

		cnt = R - L;

		//out.println(Arrays.toString(A));
		out.println(cnt);
	}

	public int[] nextIntArray(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)a[i] = nextInt();
		return a;
	}
	public long[] nextLongArray(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)a[i] = nextLong();
		return a;
	}
	public int nextInt() {
		return Integer.parseInt(next());
	}
	public long nextLong() {
		return Long.parseLong(next());
	}
	public String next() {
		return sc.next();
	}

} public class Main {
	static final PrintStream out = System.out;
	static Scanner sc = new Scanner(System.in);
	static final long Mod = 1000_000_007L;
	public static void main(String[] args) {
		Main main = new Main();
		main.solve();
		System.exit(0);
	}

	void solve() {
		int N = nextInt();
		int[] A = nextIntArray(N);

		Arrays.sort(A);

		int cnt = 0;
		if(N % 2 == 1) {
			out.println(0);
			return;
		}

		int L = A[N/2-1];
		int R = A[N/2];

		cnt = R - L;

		//out.println(Arrays.toString(A));
		out.println(cnt);
	}

	public int[] nextIntArray(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)a[i] = nextInt();
		return a;
	}
	public long[] nextLongArray(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)a[i] = nextLong();
		return a;
	}
	public int nextInt() {
		return Integer.parseInt(next());
	}
	public long nextLong() {
		return Long.parseLong(next());
	}
	public String next() {
		return sc.next();
	}

} Main
import java.io.PrintStream;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	static final PrintStream out = System.out;
	static Scanner sc = new Scanner(System.in);
	static final long Mod = 1000_000_007L;
	public static void main(String[] args) {
		Main main = new Main();
		main.solve();
		System.exit(0);
	}

	void solve() {
		int N = nextInt();
		int[] A = nextIntArray(N);

		Arrays.sort(A);

		int cnt = 0;
		if(N % 2 == 1) {
			out.println(0);
			return;
		}

		int L = A[N/2-1];
		int R = A[N/2];

		cnt = R - L;

		//out.println(Arrays.toString(A));
		out.println(cnt);
	}

	public int[] nextIntArray(int n) {
		int[] a = new int[n];
		for (int i = 0; i < n; i++)a[i] = nextInt();
		return a;
	}
	public long[] nextLongArray(int n) {
		long[] a = new long[n];
		for (int i = 0; i < n; i++)a[i] = nextLong();
		return a;
	}
	public int nextInt() {
		return Integer.parseInt(next());
	}
	public long nextLong() {
		return Long.parseLong(next());
	}
	public String next() {
		return sc.next();
	}

}