#include <bits/stdc++.h>
using namespace std;
int main() {
  int x;
  cin >> x;
  int now = 0;
  int ans = 0;
  while (true) {
    now += 2;
    ans += 2;
    if (now == x) break;
    now += 2;
    ans += 2;
    if (now == x) break;
    now--;
    ans++;
    if (now == x) break;
    now--;
    ans++;
    if (now == x) break;
    now += 2;
    ans += 2;
    if (now == x) break;
    now--;
    ans++;
    if (now == x) break;
    now--;
    ans++;
    if (now == x) break;
  }
  cout << ans << endl;
  return 0;
}