import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner koko = new Scanner(System.in);
        int n = koko.nextInt();
        long a=0;
        long[] b=new long[n];
        for(int i=0; i<=n/2; i++){
            b[i]=1;
            for(int j=0; j<i; j++){
                b[i]=b[i]*(n-i-j)/(j+1);
            }
            a=a+b[i];
        }
        System.out.println(a);
    }
}