import java.util.*

fun main(arr:Array<String>) {
    val blockCount = readLine()!!.toInt()
    val ans = getAns(blockCount)
    println(ans)
}

val dic = mutableMapOf<Int, Long>()

fun getAns(remain:Int):Long {
    if(remain == 0) {
        return 1
    }
    if(remain < 0) {
        return 0
    }
    dic[remain]?.let { return it }
    var ans = getAns(remain - 2)
    ans += getAns(remain - 1)
    dic[remain] = ans
    return ans
}