#include <bits/stdc++.h>
using namespace std;

int main(){
    int now=0,sum=0;
    int a;
cin>>a;
for(int i=1;i<100;i++){
    now+=2;sum+=2;
    if(now==a){break;}
    now+=2;sum+=2;
    if(now==a){break;}
    now--;sum++;
    if(now==a){break;}
     now--;sum++;
    if(now==a){break;}
     now+=2;sum+=2;
    if(now==a){break;}
     now--;sum++;
    if(now==a){break;}
     now--;sum++;
    if(now==a){break;}
}
cout<<sum<<endl;
}