#include<iostream>
#include<iomanip>
using namespace std;
double fibb(long n){
if(n<1){
return -1;
}
long Fn+1;
F1=1;
F2=1;
for(int i=3;i<=n;i++){
Fi=Fi-1+Fi-2;
}
return Fn;
}
int main(){
long num;
cin>>num;
if(num<20){
cout<<setprecision(8)<<fixed<<fibb(num)/fibb(num+1)<<endl;
}else{
cout<<"0.61803399"<<endl;
}
return 0;
}