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

long long n,dp[105];

int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	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];
}