use std::io::{stdin, Read};

fn main() {
    let mut buf = String::new();
    stdin().read_to_string(&mut buf).unwrap();
    let mut tok = buf.split_whitespace();
    let mut get = || tok.next().unwrap();
    macro_rules! get {
        ($t:ty) => (get().parse::<$t>().unwrap());
        () => (get!(usize));
    }
    
    let n = get!();
    
    let mut ans = 0;
    let mut vs = vec![];
    let mut g = vec![vec![false; n + 1]; n + 1];
    for i in 2..n+1 {
        for j in i+1..n+1 {
            let r = gcd(i, j) != 1;
            g[i][j] = r;
            g[j][i] = r;
        }
    }
    solve(&mut ans, &mut vs, 0, n, false, &g);
    
    println!("{}", ans);
}

fn solve(ans: &mut usize, vs: &mut Vec<usize>, sum: usize, i: usize, even: bool, g: &Vec<Vec<bool>>) {
    if i < 2 {
        if sum > *ans {
            *ans = sum;
        }
        return;
    }
    let mut ok = true;
    for &v in vs.iter() {
        if g[i][v] {
            ok = false;
            break;
        }
    }
    if ok {
        vs.push(i);
        if i % 2 == 0 {
            solve(ans, vs, sum + i, i - 1, true, g);
        } else if even {
            solve(ans, vs, sum + i, i - 2, even, g);
        } else {
            solve(ans, vs, sum + i, i - 1, even, g);
        }
        vs.pop();
    }
    if even {
        solve(ans, vs, sum, i - 2, even, g);
    } else {
        solve(ans, vs, sum, i - 1, even, g);
    }
}

// doc.rust-lang.org/std/ops/trait.Div.html
fn gcd(x: usize, y: usize) -> usize {
    let mut x = x;
    let mut y = y;
    while y != 0 {
        let t = y;
        y = x % y;
        x = t;
    }
    x
}