import java.util.*;
public class Main{
  public static void main(String[]args){
    Scanner sc = new Scanner(System.in);

    int N = sc.nextInt();
    double[] data = new double[1000];
    int v;
    double temp;
    double lenkin;

    for(int i = 0;i<N;i++){

      v  = sc.nextInt();

      data[i]=v;

    }

    for(int i = 0;i<N;i++){
      for(int j = i+1;j<N;j++){
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      }
    }

    lenkin = (data[0]+data[1])/2;

    for(int i = 2;i<N;i++){
      lenkin = (lenkin+data[i])/2;

    }

    System.out.println(lenkin);

  }
} import java.util.*; util.* java public class Main{
  public static void main(String[]args){
    Scanner sc = new Scanner(System.in);

    int N = sc.nextInt();
    double[] data = new double[1000];
    int v;
    double temp;
    double lenkin;

    for(int i = 0;i<N;i++){

      v  = sc.nextInt();

      data[i]=v;

    }

    for(int i = 0;i<N;i++){
      for(int j = i+1;j<N;j++){
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      }
    }

    lenkin = (data[0]+data[1])/2;

    for(int i = 2;i<N;i++){
      lenkin = (lenkin+data[i])/2;

    }

    System.out.println(lenkin);

  }
} Main public static void main(String[]args){
    Scanner sc = new Scanner(System.in);

    int N = sc.nextInt();
    double[] data = new double[1000];
    int v;
    double temp;
    double lenkin;

    for(int i = 0;i<N;i++){

      v  = sc.nextInt();

      data[i]=v;

    }

    for(int i = 0;i<N;i++){
      for(int j = i+1;j<N;j++){
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      }
    }

    lenkin = (data[0]+data[1])/2;

    for(int i = 2;i<N;i++){
      lenkin = (lenkin+data[i])/2;

    }

    System.out.println(lenkin);

  } main {
    Scanner sc = new Scanner(System.in);

    int N = sc.nextInt();
    double[] data = new double[1000];
    int v;
    double temp;
    double lenkin;

    for(int i = 0;i<N;i++){

      v  = sc.nextInt();

      data[i]=v;

    }

    for(int i = 0;i<N;i++){
      for(int j = i+1;j<N;j++){
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      }
    }

    lenkin = (data[0]+data[1])/2;

    for(int i = 2;i<N;i++){
      lenkin = (lenkin+data[i])/2;

    }

    System.out.println(lenkin);

  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc double[] data = new double[1000]; data new double[1000] 1000 int v; v double temp; temp double lenkin; lenkin for(int i = 0;i<N;i++){

      v  = sc.nextInt();

      data[i]=v;

    } int i = 0; int i = 0; i 0 i<N i N i++ i++ i {

      v  = sc.nextInt();

      data[i]=v;

    } {

      v  = sc.nextInt();

      data[i]=v;

    } v  = sc.nextInt() v sc.nextInt() sc.nextInt sc data[i]=v data[i] data i v for(int i = 0;i<N;i++){
      for(int j = i+1;j<N;j++){
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      }
    } int i = 0; int i = 0; i 0 i<N i N i++ i++ i {
      for(int j = i+1;j<N;j++){
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      }
    } {
      for(int j = i+1;j<N;j++){
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      }
    } for(int j = i+1;j<N;j++){
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      } int j = i+1; int j = i+1; j i+1 i 1 j<N j N j++ j++ j {
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      } {
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      } if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        } data[i]>data[j] data[i] data i data[j] data j {
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        } temp = data[i] temp data[i] data i data[i]=data[j] data[i] data i data[j] data j data[j]=temp data[j] data j temp lenkin = (data[0]+data[1])/2 lenkin (data[0]+data[1])/2 (data[0]+data[1]) data[0] data 0 data[1] data 1 2 for(int i = 2;i<N;i++){
      lenkin = (lenkin+data[i])/2;

    } int i = 2; int i = 2; i 2 i<N i N i++ i++ i {
      lenkin = (lenkin+data[i])/2;

    } {
      lenkin = (lenkin+data[i])/2;

    } lenkin = (lenkin+data[i])/2 lenkin (lenkin+data[i])/2 (lenkin+data[i]) lenkin data[i] data i 2 System.out.println(lenkin) System.out.println System.out System System.out lenkin String[]args args public class Main{
  public static void main(String[]args){
    Scanner sc = new Scanner(System.in);

    int N = sc.nextInt();
    double[] data = new double[1000];
    int v;
    double temp;
    double lenkin;

    for(int i = 0;i<N;i++){

      v  = sc.nextInt();

      data[i]=v;

    }

    for(int i = 0;i<N;i++){
      for(int j = i+1;j<N;j++){
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      }
    }

    lenkin = (data[0]+data[1])/2;

    for(int i = 2;i<N;i++){
      lenkin = (lenkin+data[i])/2;

    }

    System.out.println(lenkin);

  }
} public class Main{
  public static void main(String[]args){
    Scanner sc = new Scanner(System.in);

    int N = sc.nextInt();
    double[] data = new double[1000];
    int v;
    double temp;
    double lenkin;

    for(int i = 0;i<N;i++){

      v  = sc.nextInt();

      data[i]=v;

    }

    for(int i = 0;i<N;i++){
      for(int j = i+1;j<N;j++){
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      }
    }

    lenkin = (data[0]+data[1])/2;

    for(int i = 2;i<N;i++){
      lenkin = (lenkin+data[i])/2;

    }

    System.out.println(lenkin);

  }
} Main
import java.util.*;
public class Main{
  public static void main(String[]args){
    Scanner sc = new Scanner(System.in);

    int N = sc.nextInt();
    double[] data = new double[1000];
    int v;
    double temp;
    double lenkin;

    for(int i = 0;i<N;i++){

      v  = sc.nextInt();

      data[i]=v;

    }

    for(int i = 0;i<N;i++){
      for(int j = i+1;j<N;j++){
        if(data[i]>data[j]){
          temp = data[i];
          data[i]=data[j];
          data[j]=temp;
        }
      }
    }

    lenkin = (data[0]+data[1])/2;

    for(int i = 2;i<N;i++){
      lenkin = (lenkin+data[i])/2;

    }

    System.out.println(lenkin);

  }
}
