func main()
	var N: int :: cui@input().toInt(&)
	var dp: []int :: #[N + 2]int
	do dp[0] :: 1
	for i(0, N - 1)
		do dp[i + 1] :+ dp[i]
		do dp[i + 2] :+ dp[i]
	end for
	var ans: int :: dp[N]
	do cui@print("\{ans}\n")
end func