import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int n = Integer.parseInt(in.next());
            int d[] = new int[n];
            for (int i = 0; i < n; i++) {
                d[i] = Integer.parseInt(in.next());
            }
            Arrays.sort(d);
            int mid = n / 2;
            if (d[mid] - d[mid - 1] == 0) {
                out.println(0);
            } else {
                // 出力
                out.println(d[mid] - d[mid - 1]);
            }

        }

    }
}
 import java.io.OutputStream; OutputStream java.io import java.io.IOException; IOException java.io import java.io.InputStream; InputStream java.io import java.io.PrintWriter; PrintWriter java.io import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int n = Integer.parseInt(in.next());
            int d[] = new int[n];
            for (int i = 0; i < n; i++) {
                d[i] = Integer.parseInt(in.next());
            }
            Arrays.sort(d);
            int mid = n / 2;
            if (d[mid] - d[mid - 1] == 0) {
                out.println(0);
            } else {
                // 出力
                out.println(d[mid] - d[mid - 1]);
            }

        }

    }
} Main public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    } main {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    } InputStream inputStream = System.in; inputStream System.in System System.in OutputStream outputStream = System.out; outputStream System.out System System.out Scanner in = new Scanner(inputStream); in new Scanner(inputStream) PrintWriter out = new PrintWriter(outputStream); out new PrintWriter(outputStream) C solver = new C(); solver new C() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int n = Integer.parseInt(in.next());
            int d[] = new int[n];
            for (int i = 0; i < n; i++) {
                d[i] = Integer.parseInt(in.next());
            }
            Arrays.sort(d);
            int mid = n / 2;
            if (d[mid] - d[mid - 1] == 0) {
                out.println(0);
            } else {
                // 出力
                out.println(d[mid] - d[mid - 1]);
            }

        }

    } C public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int n = Integer.parseInt(in.next());
            int d[] = new int[n];
            for (int i = 0; i < n; i++) {
                d[i] = Integer.parseInt(in.next());
            }
            Arrays.sort(d);
            int mid = n / 2;
            if (d[mid] - d[mid - 1] == 0) {
                out.println(0);
            } else {
                // 出力
                out.println(d[mid] - d[mid - 1]);
            }

        } solve {
            // 入力
            int n = Integer.parseInt(in.next());
            int d[] = new int[n];
            for (int i = 0; i < n; i++) {
                d[i] = Integer.parseInt(in.next());
            }
            Arrays.sort(d);
            int mid = n / 2;
            if (d[mid] - d[mid - 1] == 0) {
                out.println(0);
            } else {
                // 出力
                out.println(d[mid] - d[mid - 1]);
            }

        } int n = Integer.parseInt(in.next()); n Integer.parseInt(in.next()) Integer.parseInt Integer in.next() in.next in int d[] = new int[n]; d new int[n] n for (int i = 0; i < n; i++) {
                d[i] = Integer.parseInt(in.next());
            } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
                d[i] = Integer.parseInt(in.next());
            } {
                d[i] = Integer.parseInt(in.next());
            } d[i] = Integer.parseInt(in.next()) d[i] d i Integer.parseInt(in.next()) Integer.parseInt Integer in.next() in.next in Arrays.sort(d) Arrays.sort Arrays d int mid = n / 2; mid n / 2 n 2 if (d[mid] - d[mid - 1] == 0) {
                out.println(0);
            } else {
                // 出力
                out.println(d[mid] - d[mid - 1]);
            } d[mid] - d[mid - 1] == 0 d[mid] - d[mid - 1] d[mid] d mid d[mid - 1] d mid - 1 mid 1 0 {
                out.println(0);
            } out.println(0) out.println out 0 {
                // 出力
                out.println(d[mid] - d[mid - 1]);
            } out.println(d[mid] - d[mid - 1]) out.println out d[mid] - d[mid - 1] d[mid] d mid d[mid - 1] d mid - 1 mid 1 int testNumber testNumber Scanner in in PrintWriter out out public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int n = Integer.parseInt(in.next());
            int d[] = new int[n];
            for (int i = 0; i < n; i++) {
                d[i] = Integer.parseInt(in.next());
            }
            Arrays.sort(d);
            int mid = n / 2;
            if (d[mid] - d[mid - 1] == 0) {
                out.println(0);
            } else {
                // 出力
                out.println(d[mid] - d[mid - 1]);
            }

        }

    }
} public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int n = Integer.parseInt(in.next());
            int d[] = new int[n];
            for (int i = 0; i < n; i++) {
                d[i] = Integer.parseInt(in.next());
            }
            Arrays.sort(d);
            int mid = n / 2;
            if (d[mid] - d[mid - 1] == 0) {
                out.println(0);
            } else {
                // 出力
                out.println(d[mid] - d[mid - 1]);
            }

        }

    }
} Main
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            // 入力
            int n = Integer.parseInt(in.next());
            int d[] = new int[n];
            for (int i = 0; i < n; i++) {
                d[i] = Integer.parseInt(in.next());
            }
            Arrays.sort(d);
            int mid = n / 2;
            if (d[mid] - d[mid - 1] == 0) {
                out.println(0);
            } else {
                // 出力
                out.println(d[mid] - d[mid - 1]);
            }

        }

    }
}

