#define _CRT_SECURE_NO_WARNINGS

#include <iostream>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <string>
#include <math.h>
#include <functional>
#include <algorithm>
#include <utility>

typedef long long Int;
#define REP(i,n) for(int i = 0 ; i < n ; ++i)
#define REPS(a,i,n) for(int i = a ; i < n ; ++i)
using namespace std;

int tile[20][20];


int main(){
	int n;
	while (cin >> n){
		if (n == 1)
			cout << 2 << endl;
		else
			cout << n - 2 + 2 * n << endl;
	}

	return 0;
}