#include<iostream> #include<iomanip> using namespace std; int main(){ int n; cin>>n; double sum=0.0; int a=2; int b=1; for(int i=1;i<=n;++i){ sum+=(double)a/b; int next_a=a+b; int next_b=a; a=next_a; b=next_b; } cout<<fixed<<setprecision(4); cout<<sum<<endl; return 0; }