#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<string>
using namespace std;
double a[101]={1.00,1.00,2.00,3.00,5.00,8.00,13.00,21.00,34.00,55.00,89.00,144.00,233.00,377.00,610.00,987.00,1597.00,2584.00,4181.00,6765.00,10946.00,17711.00,28657.00,46368.00,75025.00,121393.00,196418.00,317811.00,514229.00,832040.00,1346269.00,2178309.00,3524578.00,5702887.00,9227465.00,14930352.00,24157817.00,39088169.00,63245986.00,102334155.00,165580141.00,267914296.00,433494437.00,701408733.00,1134903170.00,1836311903.00,2971215073.00,4807526976.00};
int main()
{
    int n;
    cin>>n;
    printf("%.2lf\n",a[n-1]);
    return 0;
}