#include <bits/stdc++.h>
using namespace std;
long long dp[10005];
int main(){
	long long n;
	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];
}