#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,i; double sum,a,b,c; a=2,b=1,sum=0; cin>>n; for(int i=1;i<=n;i++){ sum+=a/b; c=a; a=a+b; b=c; } cout<<sum<<endl; return 0; }