#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

int main(){
	
	int X;
	cin>>X;
	
	string S = "AABBABB";
	
	int sum = 0;
	int cur = 0;
	rep(i,100000000){
		int ii = i%S.size();
		if(S[ii]=='A'){
			sum += 2;
			cur += 2;
		}
		else{
			sum += 1;
			cur --;
		}
		if(cur==X){
			cout<<sum<<endl;
			return 0;
		}
	}
	
    return 0;
}