fun main(args: Array<String>) {
    val n = readLine()!!.toInt()
    val list: MutableList<Long> = mutableListOf()
    list.add(1)
    list.add(1)

    for (i in 2..n) {
        list.add(list[i-1] + list[i-2])
    }

    println(list[n])
}