import java.util.Scanner;

public class Main {

    private int getTotalCount(int n) {
        int[] f = new int[n + 1];
        f[0] = 0;
        f[1] = 1;
        for (int i = 2; i <= n; i++) {
            f[i] = f[i-2] + f[i-1];
        }
        return f[n];
    }

    public Main() {
        Scanner in = new Scanner(System.in);
        while (in.hasNextInt()) {
            int monthCount = in.nextInt();
            int result = getTotalCount(monthCount);
            System.out.println(result);
        }
    }

    public static void main(String[] args) {
        Main solution = new Main();
    }
}