#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;

int main(){
    ll dp[100],N;
    cin >> N;
    for(int i=0;i<100;i++)dp[i] = 0;
    dp[0] = 1;
    dp[1] = 1;
    for(int i=2;i<100;i++)dp[i] = dp[i-1] + dp[i-2];
    cout << dp[N] << endl;
    return 0;
}