#include <bits/stdc++.h>

using namespace std;

int f[50] = { 0, 1};

 int main() {

	 int n;
     
    cin >> n;
    
    for (int i = 2; i <= n; i++)
    
    {
        f[i] = f[i - 1] + f[i - 2];
    }
    cout << f[n] << ".00";
    return 0;
}