#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=2,fm=1,a,s=0; int n; cin>>n; for(int i=1;i<=n;i++){ s+=fz/fm; a=fz; fz=fz+fm; fm=a; } cout<<s; return 0; }