#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
    
    int x;cin>>x;
    
    string str ="AABBABB";
    
    int now = 0;
    int dist = 0;
    while(1){
        for(int i=0;i<str.size();i++){
            if(str[i]=='A') {
                now+=2;
                dist+=2;
            }else {
                now-=1;
                dist+=1;
            }
            if(now==x) {
                cout << dist << endl;
                return 0;
            }
        }
    }
}