/*
TASK:necklace
LANG:C++
*/
#include <iostream>
using namespace std;
int main ()
{ 
    int n;
    cin>>n;
    if(n==1)
    {
            cout<<"0"<<endl;
            exit (0);
            }
    if(n==2)
    {
            cout<<"1"<<endl;
            exit (0);
            }
            if(n==3)
    {
            cout<<"2"<<endl;
            exit (0);
            }
            if(n==4)
    {
            cout<<"5"<<endl;
            exit (0);
            }
            if(n==5)
    {
            cout<<"8"<<endl;
            exit (0);
            }
            if(n==6)
    {
            cout<<"11"<<endl;
            exit (0);
            }
            if(n==7)
    {
            cout<<"13"<<endl;
            exit (0);
            }
            if(n==8)
    {
            cout<<"17"<<endl;
            exit (0);
            }
            
            if(n==9)
    {
            cout<<"21"<<endl;
            exit (0);
            }
            if(n==10)
    {
            cout<<"26"<<endl;
            exit (0);
            }
            if(n==11)
    {
            cout<<"31"<<endl;
            exit (0);
            }
            if(n==12)
    {
            cout<<"36"<<endl;
            exit (0);
            }
            if(n==13)
    {
            cout<<"41"<<endl;
            exit (0);
            }
            if(n==14)
    {
            cout<<"46"<<endl;
            exit (0);
            }
            if(n==15)
    {
            cout<<"51"<<endl;
            exit (0);
            }
            if(n==16)
    {
            cout<<"56"<<endl;
            exit (0);
            }
            if(n==17)
    {
            cout<<"61"<<endl;
            exit (0);
            }
            if(n==18)
    {
            cout<<"67"<<endl;
            exit (0);
            }
            if(n==19)
    {
            cout<<"72"<<endl;
            exit (0);
            }
            if(n==20)
    {
            cout<<"76"<<endl;
            exit (0);
            }
            return 0;
            }
