fn main() {
    let mut x = String::new();
    std::io::stdin().read_line(&mut x).ok();
    let x: usize = x.trim().parse().unwrap();

    let mut result = 0usize;
    let mut pos = 0usize;
    for _ in 0..100 {
        for &i in vec![0,0,1,1,0,1,1].iter() {
            if i == 0 {
                pos += 2;
                result += 2;
            } else {
                pos -= 1;
                result += 1;
            }
            if pos == x {
                println!("{}", result);
                return;
            }
        }
    }
}