import java.util.*;

public class Main {
	
	public static void main(String[] args)  {
		Scanner scan = new Scanner(System.in);
		
		int n=Integer.parseInt(scan.next());
		double[]v=new double [n];
		for (int i=0;i<n;++i) {
			v[i]=Double.parseDouble(scan.next());
		}
		Arrays.parallelSort(v);
		
		double sum=0;
		for(int i=0;i<n;++i) {
			if (i==0) {
				sum+=(v[i]+v[i+1])/2;
				
			}else if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			}
			
		}
		
		System.out.print(sum);
}
}
//end import java.util.*; util.* java public class Main {
	
	public static void main(String[] args)  {
		Scanner scan = new Scanner(System.in);
		
		int n=Integer.parseInt(scan.next());
		double[]v=new double [n];
		for (int i=0;i<n;++i) {
			v[i]=Double.parseDouble(scan.next());
		}
		Arrays.parallelSort(v);
		
		double sum=0;
		for(int i=0;i<n;++i) {
			if (i==0) {
				sum+=(v[i]+v[i+1])/2;
				
			}else if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			}
			
		}
		
		System.out.print(sum);
}
} Main public static void main(String[] args)  {
		Scanner scan = new Scanner(System.in);
		
		int n=Integer.parseInt(scan.next());
		double[]v=new double [n];
		for (int i=0;i<n;++i) {
			v[i]=Double.parseDouble(scan.next());
		}
		Arrays.parallelSort(v);
		
		double sum=0;
		for(int i=0;i<n;++i) {
			if (i==0) {
				sum+=(v[i]+v[i+1])/2;
				
			}else if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			}
			
		}
		
		System.out.print(sum);
} main {
		Scanner scan = new Scanner(System.in);
		
		int n=Integer.parseInt(scan.next());
		double[]v=new double [n];
		for (int i=0;i<n;++i) {
			v[i]=Double.parseDouble(scan.next());
		}
		Arrays.parallelSort(v);
		
		double sum=0;
		for(int i=0;i<n;++i) {
			if (i==0) {
				sum+=(v[i]+v[i+1])/2;
				
			}else if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			}
			
		}
		
		System.out.print(sum);
} Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int n=Integer.parseInt(scan.next()); n Integer.parseInt(scan.next()) Integer.parseInt Integer scan.next() scan.next scan double[]v=new double [n]; v new double [n] n for (int i=0;i<n;++i) {
			v[i]=Double.parseDouble(scan.next());
		} int i=0; int i=0; i 0 i<n i n ++i ++i i {
			v[i]=Double.parseDouble(scan.next());
		} {
			v[i]=Double.parseDouble(scan.next());
		} v[i]=Double.parseDouble(scan.next()) v[i] v i Double.parseDouble(scan.next()) Double.parseDouble Double scan.next() scan.next scan Arrays.parallelSort(v) Arrays.parallelSort Arrays v double sum=0; sum 0 for(int i=0;i<n;++i) {
			if (i==0) {
				sum+=(v[i]+v[i+1])/2;
				
			}else if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			}
			
		} int i=0; int i=0; i 0 i<n i n ++i ++i i {
			if (i==0) {
				sum+=(v[i]+v[i+1])/2;
				
			}else if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			}
			
		} {
			if (i==0) {
				sum+=(v[i]+v[i+1])/2;
				
			}else if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			}
			
		} if (i==0) {
				sum+=(v[i]+v[i+1])/2;
				
			}else if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			} i==0 i 0 {
				sum+=(v[i]+v[i+1])/2;
				
			} sum+=(v[i]+v[i+1])/2 sum (v[i]+v[i+1])/2 (v[i]+v[i+1]) v[i] v i v[i+1] v i+1 i 1 2 if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			} i==1 i 1 continue; {
				sum=(sum+v[i])/2;
			} sum=(sum+v[i])/2 sum (sum+v[i])/2 (sum+v[i]) sum v[i] v i 2 System.out.print(sum) System.out.print System.out System System.out sum String[] args args public class Main {
	
	public static void main(String[] args)  {
		Scanner scan = new Scanner(System.in);
		
		int n=Integer.parseInt(scan.next());
		double[]v=new double [n];
		for (int i=0;i<n;++i) {
			v[i]=Double.parseDouble(scan.next());
		}
		Arrays.parallelSort(v);
		
		double sum=0;
		for(int i=0;i<n;++i) {
			if (i==0) {
				sum+=(v[i]+v[i+1])/2;
				
			}else if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			}
			
		}
		
		System.out.print(sum);
}
} public class Main {
	
	public static void main(String[] args)  {
		Scanner scan = new Scanner(System.in);
		
		int n=Integer.parseInt(scan.next());
		double[]v=new double [n];
		for (int i=0;i<n;++i) {
			v[i]=Double.parseDouble(scan.next());
		}
		Arrays.parallelSort(v);
		
		double sum=0;
		for(int i=0;i<n;++i) {
			if (i==0) {
				sum+=(v[i]+v[i+1])/2;
				
			}else if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			}
			
		}
		
		System.out.print(sum);
}
} Main
import java.util.*;

public class Main {
	
	public static void main(String[] args)  {
		Scanner scan = new Scanner(System.in);
		
		int n=Integer.parseInt(scan.next());
		double[]v=new double [n];
		for (int i=0;i<n;++i) {
			v[i]=Double.parseDouble(scan.next());
		}
		Arrays.parallelSort(v);
		
		double sum=0;
		for(int i=0;i<n;++i) {
			if (i==0) {
				sum+=(v[i]+v[i+1])/2;
				
			}else if (i==1)continue;
			
			else {
				sum=(sum+v[i])/2;
			}
			
		}
		
		System.out.print(sum);
}
}
//end