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);
        ABC138_c solver = new ABC138_c();
        solver.solve(1, in, out);
        out.close();
    }

    static class ABC138_c {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int N = in.nextInt();
            int[] v = new int[N];
            for (int i = 0; i < N; i++) {
                v[i] = in.nextInt();

            }
            Arrays.sort(v);
            double ans = 0;
            for (int i = 1; i < N; i++) {
                if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                }

            }
            out.println(ans);
        }

    }
}
 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);
        ABC138_c solver = new ABC138_c();
        solver.solve(1, in, out);
        out.close();
    }

    static class ABC138_c {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int N = in.nextInt();
            int[] v = new int[N];
            for (int i = 0; i < N; i++) {
                v[i] = in.nextInt();

            }
            Arrays.sort(v);
            double ans = 0;
            for (int i = 1; i < N; i++) {
                if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                }

            }
            out.println(ans);
        }

    }
} 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);
        ABC138_c solver = new ABC138_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);
        ABC138_c solver = new ABC138_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) ABC138_c solver = new ABC138_c(); solver new ABC138_c() solver.solve(1, in, out) solver.solve solver 1 in out out.close() out.close out String[] args args static class ABC138_c {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int N = in.nextInt();
            int[] v = new int[N];
            for (int i = 0; i < N; i++) {
                v[i] = in.nextInt();

            }
            Arrays.sort(v);
            double ans = 0;
            for (int i = 1; i < N; i++) {
                if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                }

            }
            out.println(ans);
        }

    } ABC138_c public void solve(int testNumber, Scanner in, PrintWriter out) {
            int N = in.nextInt();
            int[] v = new int[N];
            for (int i = 0; i < N; i++) {
                v[i] = in.nextInt();

            }
            Arrays.sort(v);
            double ans = 0;
            for (int i = 1; i < N; i++) {
                if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                }

            }
            out.println(ans);
        } solve {
            int N = in.nextInt();
            int[] v = new int[N];
            for (int i = 0; i < N; i++) {
                v[i] = in.nextInt();

            }
            Arrays.sort(v);
            double ans = 0;
            for (int i = 1; i < N; i++) {
                if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                }

            }
            out.println(ans);
        } int N = in.nextInt(); N in.nextInt() in.nextInt in int[] v = new int[N]; v new int[N] N for (int i = 0; i < N; i++) {
                v[i] = in.nextInt();

            } int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
                v[i] = in.nextInt();

            } {
                v[i] = in.nextInt();

            } v[i] = in.nextInt() v[i] v i in.nextInt() in.nextInt in Arrays.sort(v) Arrays.sort Arrays v double ans = 0; ans 0 for (int i = 1; i < N; i++) {
                if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                }

            } int i = 1; int i = 1; i 1 i < N i N i++ i++ i {
                if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                }

            } {
                if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                }

            } if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                } i == 1 i 1 {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } ans = (v[i - 1] + v[i]) * 0.5 ans (v[i - 1] + v[i]) * 0.5 (v[i - 1] + v[i]) v[i - 1] v i - 1 i 1 v[i] v i 0.5 {
                    ans = (ans + v[i]) * 0.5;
                } ans = (ans + v[i]) * 0.5 ans (ans + v[i]) * 0.5 (ans + v[i]) ans v[i] v i 0.5 out.println(ans) out.println out ans 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);
        ABC138_c solver = new ABC138_c();
        solver.solve(1, in, out);
        out.close();
    }

    static class ABC138_c {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int N = in.nextInt();
            int[] v = new int[N];
            for (int i = 0; i < N; i++) {
                v[i] = in.nextInt();

            }
            Arrays.sort(v);
            double ans = 0;
            for (int i = 1; i < N; i++) {
                if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                }

            }
            out.println(ans);
        }

    }
} 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);
        ABC138_c solver = new ABC138_c();
        solver.solve(1, in, out);
        out.close();
    }

    static class ABC138_c {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int N = in.nextInt();
            int[] v = new int[N];
            for (int i = 0; i < N; i++) {
                v[i] = in.nextInt();

            }
            Arrays.sort(v);
            double ans = 0;
            for (int i = 1; i < N; i++) {
                if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                }

            }
            out.println(ans);
        }

    }
} 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);
        ABC138_c solver = new ABC138_c();
        solver.solve(1, in, out);
        out.close();
    }

    static class ABC138_c {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int N = in.nextInt();
            int[] v = new int[N];
            for (int i = 0; i < N; i++) {
                v[i] = in.nextInt();

            }
            Arrays.sort(v);
            double ans = 0;
            for (int i = 1; i < N; i++) {
                if (i == 1) {

                    ans = (v[i - 1] + v[i]) * 0.5;
                } else {
                    ans = (ans + v[i]) * 0.5;
                }

            }
            out.println(ans);
        }

    }
}

