import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.TreeSet;
public class Main {
	public static int w;
	public static int k;
	public static int n;
//	public static int[][] dp;
	public static int[] a;
	public static int[] b;
	public static List<double[]> list = new ArrayList<double[]>();
	public static TreeSet<Integer> set = new TreeSet<Integer>();
//	public static PriorityQueue<Integer> pq = new PriorityQueue<Integer>();
	public static void main(String[] args) throws NumberFormatException, IOException{

		ContestScanner in = new ContestScanner();
		n = in.nextInt();
		long[] dp = new long[n+1];
		dp[0] = 1;
		dp[1] = 1;
		for(int i=2; i<=n; i++){
			dp[i] = dp[i-1] + dp[i-2];
		}
		System.out.println(dp[n]);
	}
	
}



class Node{
	int id;
	List<Node> edge = new ArrayList<Node>();
	public Node(int id){
		this.id = id;
	}
	public void createEdge(Node node){
		edge.add(node);
	}
}

class MyMath{
	public static long fact(long n){
		long res = 1;
		while(n > 0){
			res *= n--;
		}
		return res;
	}
	public static long[][] pascalT(int n){
		long[][] tri = new long[n][];
		for(int i=0; i<n; i++){
			tri[i] = new long[i+1];
			for(int j=0; j<i+1; j++){
				if(j == 0 || j == i){
					tri[i][j] = 1;
				}else{
					tri[i][j] = tri[i-1][j-1] + tri[i-1][j];
				}
			}
		}
		return tri;
	}
}

class MyComp implements Comparator<Integer>{
	public int compare(Integer arg0, Integer arg1) {
		return arg0 - arg1;
	}
}
//
//class MyCompB implements Comparator<int[]>{
//	public int compare(int[] arg0, int[] arg1) {
//		return arg0[1] - arg1[1];
//	}
//}

class ContestScanner{
	private BufferedReader reader;
	private String[] line;
	private int idx;
	public ContestScanner() throws FileNotFoundException{
		reader = new BufferedReader(new InputStreamReader(System.in));
	}
	
	public String nextToken() throws IOException{
		if(line == null || line.length <= idx){
			line = reader.readLine().trim().split(" ");
			idx = 0;
		}
		return line[idx++];
	}
	
	public long nextLong() throws IOException, NumberFormatException{
		return Long.parseLong(nextToken());
	}
	
	public int nextInt() throws NumberFormatException, IOException{
		return (int)nextLong();
	}
	
	public double nextDouble() throws NumberFormatException, IOException{
		return Double.parseDouble(nextToken());
	}
}