fun main(args: Array<String>) = p34()

fun p34() {
    val n = readLine()!!.toInt()

    val dp = LongArray(45)
    dp[0] = 1
    dp[1] = 1

    for (i in 2..n) dp[i] = dp[i - 1] + dp[i - 2]

    val answer = dp[n]

    println(answer)
}

