#include <iostream>
#include <cassert>
using namespace std;

class Fibonacci final {
public:
    static int get(int n) {
        assert(n >= 0);
        int* fib = new int[n];
        fib[0] = 1;
        fib[1] = 1;
        for (int i = 2; i < n; i++) {
            fib[i] = fib[i - 1] + fib[i - 2];
        }
        return fib[n - 1];
    }
};

int main(void) {
    int n;
    std::cin >> n;
    std::cout << Fibonacci::get(n) << std::endl;
    system("PAUSE");
    return 0;
}