#include "bits/stdc++.h"
using namespace std;

int main() {
	int N;
	long long dp[100];
	cin >> N;
	dp[0] = 1;
	dp[1] = 1;
	for (int i = 2; i <= N; i++)
	{
		dp[i] = dp[i - 1] + dp[i - 2];
	}
	cout << dp[N] << endl;
}