#10870

#include<iostream>
using namespace std;


int fibo(int n) {
	if (n == 0)
		return 0;
	else if (n == 1)
		return 1;
	else if (n >= 2) {
		return fibo(n - 1) + fibo(n - 2);
	}

}

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