#include<iostream>
#include<cmath>
#include<algorithm>
#include<string>
#include<map>
using namespace std;
int main() {
    int n;
    while (cin >> n) {
        long long arr[100];
        arr[1] = 1, arr[2] = 2;
        for (int i = 3;i <= n;i++) {
            arr[i] = arr[i - 1] + arr[i - 2];
        }
        cout << arr[n] << endl;
    }
    return 0;
}