#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(){ int n; cin>>n; double fz=2,fm=1,sum=fz/fm,fm0,fz0; for(int i=2;i<=n;i++){ fm0=fm; fz0=fz; fz=fm0+fz0; fm=fz0; sum+=fz/fm; } printf("%lf",sum); return 0; }