public static void main(String args[]){    
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] fb = new int[10000];
    fb[0] = 1;
    fb[1] = 1;
    for(int i = 0; i < n; i++){
        fb[i + 2] = fb[i] + fb[i + 1];
    }         
    System.out.println(fb[n - 1]);
    }
//----------------------------------------------------
    public static void main(String args[]){  
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    System.out.println(fb(n - 1));
    }
    public static int fb(int n){
    if(n == 1 || n == 0){
        return 1;
    }else{
        return fb(n - 1) + fb(n - 2);
    }
    }