#include <iostream>

using namespace std;
int F(int N) {
    if (N == 0 || N == 1) return N;
    return F(N - 1) + F(N - 2);
}
int main() {
    int N;
    while (scanf("%d", &N) != EOF) {
        cout << F(N);
    }
    return 0;
}