package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)

func Scanner() string {
	sc.Scan()
	return sc.Text()
}
func main() {
	buf := make([]byte, 0)
	sc.Buffer(buf, 100000007)
	sc.Split(bufio.ScanWords)
	n, _ := strconv.Atoi(Scanner())

	dp := make([]int, n+1)

	dp[0] = 1

	for i := 0; i < n; i++ {
		dp[i+1] += dp[i]
		if i+2 <= n {
			dp[i+2] += dp[i]
		}
	}
	fmt.Println(dp[n])
}