#include<iostream> using namespace std; int main() { int fz=2,fm=1,fz0=0,fm0=0,n; double sum=0; cin>>n; for(int i=1;i<=n;i++){ sum+=fz*1.0/fm; fz0=fz; fm0=fm; fz=fz0+fm0; fm=fz0; } printf("%.4lf",sum); return 0; }