import java.util.*;
public class fibonacci_dp {
	static int[] dp=new int[100000];
	public static void main (String[] args){
		dp[0]=1; dp[1]=1;
		for (int i=2;i<100000;i++){
			dp[i]=dp[i-1]+dp[i-2];
		}
		Scanner input=new Scanner (System.in);
		int num=input.nextInt();
		System.out.format("%d\n",dp[num]);
	}
}