import java.math.BigInteger;  
import java.util.Scanner;  
  
public class Main {  
    public static void main(String[] args) {  
        Scanner cin = new Scanner(System.in);  
        int n;

        
        while(cin.hasNext()){
        BigInteger a = BigInteger.ONE;
        BigInteger b = BigInteger.ONE;
            n=cin.nextInt();
                   
            if(n==1) System.out.println("1");
            else{
                for(int i=2;i<=n;i++){
                    BigInteger c = a.add(b);
                    a=b;
                    b=c;
                }
                System.out.println(b);
            }
        }
    }  
}