#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 n,fm,fz,fm1=1,fz1=2,sum=0; cin>>n; for(int i=1;i<=n;i++){ fm=fz1; fz=fz1+fm1; sum+=fz/fm; fm1=fm; fz1=fz; } cout<<sum; return 0; }