#include <iostream>
using namespace std;

int fibo(int n);

int main() {
    int n;
    cin >> n;
    cout << fibo(n) << endl;
    return 0;
}

int fibo(int n) {
    if (n == 1 || n == 2) {
        return 1;
    }
    return fibo(n - 1) + fibo (n-2);
}