fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn extract_primes(n: usize) -> Vec<usize> {
    let mut is_prime = vec![true; n];
    let mut primes = Vec::new();
    is_prime[0] = false;
    is_prime[1] = false;

    for i in 2..n {
        if is_prime[i] {
            primes.push(i);
            let mut j = 2 * i;
            while j < n {
                is_prime[j] = false;
                j += i;
            }
        }
    }
    primes
}

fn main() {
    let n: usize = read();
    // let n = 10000;
    let primes = extract_primes(n + 1);
    let mut dp = vec![-1; n + 1];

    for p in primes {
        // println!("{:?}", dp);
        for i in (0..dp.len()).rev() {
            if dp[i] != - 1 && i + p < n + 1 {
                dp[i + p] = std::cmp::max(dp[i + p], dp[i] + 1);
            }
        }
        dp[p] = std::cmp::max(1, dp[p]);
    }
    println!("{:?}", dp[n]);
}