import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] m = new int[n];
        for(int m_i=0; m_i < n; m_i++){
            m[m_i] = in.nextInt();
        }
        // your code goes here
        System.out.println(count(n));
    }
    
    private static int count(int n){
        if(n == 1 || n==2){
            return 1;
        }
        
        int num = 1;
        //odd n
        if(n%2 != 0){
            for(int i=2; i<n; i++){
                if((n-i) == (i+1)){
                    i++;
                }
                num += fact(n)/(fact(n-i)*fact(i));
            }
        }
        
        //even n
        else {
            for(int i=2; i<n; i++){
                if(i == n/2){
                    num += (fact(n)/(fact(n-i)*fact(i))) / 2;
                }
                else{
                    num += fact(n)/(fact(n-i)*fact(i));
                }
            }
        }
        return num;
    }
    
    private static int fact(int n){
        if(n==1 || n==0){
            return 1;
        } 
        return n*fact(n-1);
    }
}