import java.util.*

fun main(args: Array<String>) {


    var sc = Scanner(System.`in`)

    val n = sc.nextInt()
    
    val dp = IntArray(n+1)
    
    dp[0] = 1
    dp[1] = 1
    
    for(i in 2..n){
        dp[i] = dp[i-1] + dp[i-2]
    }
    
    println(dp[n])

}


