#include <bits/stdc++.h>
using namespace std;
int a[10010];
int main() {
	int n;
	cin >> n;
	a[0] = 0;
	a[1] = 1;
	a[2] = 1;
	for (int i = 3; i <= n; ++i) {
		a[i] = a[i - 1] + a[i - 2];
	}
	cout << a[n] << ".00" << endl;
	return 0;
}

记录详细：https://www.luogu.com.cn/record/188055930