#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ double fz,fz0=2,fm,fm0=1,h=2; int n; cin>>n; for(int i=2;i<=n;++i){ fm=fz0; fz=fm0+fz0; h+=fz/fm; fm0=fm; fz0=fz; } printf("%.4lf",h); return 0; }