#include <iostream>
using namespace std;
int fibonacci(int n)
{
	if (n < 2) return 1;
	else return fibonacci(n - 1) + fibonacci(n - 2);
}
int main()
{
	int n;
	cin >> n;
	cout << fibonacci(n - 1) << endl;
	return 0;
} 

// #1 #3 #4 AC
// #2 #5 #6 #7 #8 #9 #10 WA