import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();

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