#include<iostream> #include<cstdio> #include<cstring> #include<cmath> using namespace std; double n,fm,fz,fm0=1,fz0=2,s=2; int main(){ cin>>n; for(int i=2;i<=n;i++) { fm=fz0; fz=fm0+fz0; s+=fz/fm; fm0=fm; fz0=fz; } printf("%.4lf",s); }