fun main(args: Array<String>) {
    val n = readLine()!!.toInt()
    var arr = Array(n+1) { 0L }
    arr[0] = 1
    arr[1] = 1

    for (i in 2..n) {
        arr[i] = arr[i-1] + arr[i-2]
    }

    println(arr[n])
}