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