import java.math.BigInteger;
import java.util.*;
public class Main {
    static BigInteger [][] record =  new BigInteger[201][101];
    public static BigInteger combine(int m, int n) {
        if(record[m][n] != null) return record[m][n];
        if (n == 0 || m == n) {
            record[m][n] = new BigInteger("1");
            return record[m][n];
        } else {
            BigInteger tmp1, tmp2;
            if (record[m - 1][n - 1] != null)
                tmp1 = record[m - 1][n - 1];
            else
                tmp1 = combine(m - 1, n - 1);
            if (record[m - 1][n] != null)
                tmp2 = record[m - 1][n];
            else
                tmp2 = combine(m - 1, n);
            BigInteger tmp = tmp1.add(tmp2);
            record[m][n] = tmp;
            return tmp;
        }
    }
    
    public static void main(String[] args) {
        
        Scanner cin = new Scanner(System.in);
        while(cin.hasNext()) {
            int N = cin.nextInt();
            BigInteger s = BigInteger.ZERO;
            for (int i = 0; i <= N/2; i++) {
                int j = N - i * 2;
                s = s.add(combine(i + j, Math.min(i, j)));
            }
            System.out.println(s);
        }
        cin.close();
    }
}