content: package v110;
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.Arrays;
  import java.util.StringTokenizer;
  
  public class AGraphProblem_UVa11069 {
  	
  	static int[][] memo;
  	
  	static int dp(int n, int s)
  	{
  		if(n <= 0)
  			return 1;
  		if(memo[n][s] != -1)
  			return memo[n][s];
  		int take = 0, leave = 0;
  		take = dp(n - 2, 0);
  		
  		if(s == 0 && n != 1)
  			leave = dp(n - 1, 1);
  		return memo[n][s] = take + leave;
  	}
  	public static void main(String[] args) throws IOException {
  
  		Scanner sc = new Scanner(System.in);
  		PrintWriter out = new PrintWriter(System.out);
  	
  		memo = new int[77][2];
  		for(int i = 0; i <= 76; ++i)
  			Arrays.fill(memo[i], -1);
  		while(sc.ready())
  			out.println(dp(sc.nextInt(), 0));
  		out.flush();
  	}
  	
  	
  	
  
  	static class Scanner 
  	{
  		StringTokenizer st;
  		BufferedReader br;
  
  		public Scanner(InputStream s){	br = new BufferedReader(new InputStreamReader(s));}
  
  		public String next() throws IOException 
  		{
  			while (st == null || !st.hasMoreTokens()) 
  				st = new StringTokenizer(br.readLine());
  			return st.nextToken();
  		}
  
  		public int nextInt() throws IOException {return Integer.parseInt(next());}
  		
  		public long nextLong() throws IOException {return Long.parseLong(next());}
  
  		public String nextLine() throws IOException {return br.readLine();}
  		
  		public double nextDouble() throws IOException
  		{
  			String x = next();
  			StringBuilder sb = new StringBuilder("0");
  			double res = 0, f = 1;
  			boolean dec = false, neg = false;
  			int start = 0;
  			if(x.charAt(0) == '-')
  			{
  				neg = true;
  				start++;
  			}
  			for(int i = start; i < x.length(); i++)
  				if(x.charAt(i) == '.')
  				{
  					res = Long.parseLong(sb.toString());
  					sb = new StringBuilder("0");
  					dec = true;
  				}
  				else
  				{
  					sb.append(x.charAt(i));
  					if(dec)
  						f *= 10;
  				}
  			res += Long.parseLong(sb.toString()) / f;
  			return res * (neg?-1:1);
  		}
  		
  		public boolean ready() throws IOException {return br.ready();}
  
  
  	}
  }
  