const MOD: u64 = 1000003;
fn main() {
    proconio::input! {
        n: u64,
    }
    let primes = create_primes(20001);
    let mut dp = vec![-1; 20001];
    dp[0] = 0;
    for p in primes {
        for i in (0..dp.len()).rev() {
            if dp[i] >= 0 && (i + p as usize) < dp.len() {
                dp[i + p as usize] = std::cmp::max(dp[i + p as usize], dp[i] + 1);
            }
        }
    }
    println!("{}", dp[n as usize]);
}

fn create_primes(n: u64) -> Vec<u64> {
    let mut primes = vec![true; n as usize];
    primes[0] = false;
    primes[1] = false;
    for i in 2..n {
        if primes[i as usize] {
            for j in (i * i..n).step_by(i as usize) {
                primes[j as usize] = false;
            }
        }
    }
    primes
        .into_iter()
        .enumerate()
        .filter(|(_, prime)| *prime)
        .map(|(i, _)| i as u64)
        .collect()
}