import java.math.BigInteger;
import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        Scanner sn = new Scanner(System.in);
        while(sn.hasNext()){
            int n = sn.nextInt();
            BigInteger c = new BigInteger("1");
            long two = 1;
            for(int x = n-2;x>=0;x-=2){
                BigInteger t = new BigInteger("1");
                BigInteger tt = new BigInteger("1");
                for(int y = x+1;y<=two+x;y++){
                    t = t.multiply(new BigInteger(y+""));
                }
                for(int y = 1;y<=two;y++){
                    tt = tt.multiply(new BigInteger(y+""));
                }
                c = c.add(t.divide(tt));
                two++;
            }
            System.out.println(c.toString());
        }
        sn.close();
    }
}