import java.math.BigInteger;
import java.util.Scanner;

public class MainBigInts {
    private static BigInteger fibonacci2(int n) {
        BigInteger a = new BigInteger("2");
        BigInteger b = new BigInteger("1");
        BigInteger suma = new BigInteger("0");
        BigInteger temp = new BigInteger("0");


        if (n == 0) {
            return BigInteger.valueOf(1);
        } else {
            if (n == 1) {
                return BigInteger.valueOf(2);
            } else {
                for (int i = 2; i <= n; i++) {
                    temp = a;
                    a = a.add(b);
                    b = temp;
                }
            }
        }
        return a;
    }

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        do {
            System.out.print("Dana: ");
            int a = scanner.nextInt();
            System.out.println(fibonacci2(a));
        } while (true);

    }
}