1.6-2

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

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        BigInteger f1 = BigInteger.ONE;
        BigInteger f0 = BigInteger.ZERO;
        if (num==0){ System.out.println(f0); }
        else{
            if (num==1){ System.out.println(f1); }
            else{
                for (int i = 1;i<=num;++i) {
                    BigInteger f = f0.add(f1);
                    f0 = f1;
                    f1 = f;
                }
                System.out.println(f0);
            }
        }
    }
}