#include<iostream> #include<cstdio> using namespace std; int main(){ int fz=2,fm=1,t; double sum=0; int n; cin>>n; for(int i=1;i<=n;i++){ sum=sum+fz*1.0/fm; t=fm; fm=fz; fz=fz+t; } printf("%.4lf",sum); return 0; }