#include"iostream"
using namespace std;
int main()
{
	int n;
	cin >> n;
	int dp[50];
	int i;
	dp[0] = dp[1] = 1;
	for (i = 2; i < 50; ++i)
		dp[i] = dp[i - 1] + dp[i - 2];
	cout << dp[n] << endl;
	return 0;
}
