fn get_primes(n: usize) -> Vec<bool> {
    let mut flgs = vec![true; n+1];
    flgs[0] = false;
    flgs[1] = false;

    for i in 2..=(n as f64).sqrt().ceil() as usize {
        if !flgs[i] { continue; }
        for j in i..=n/i {
            flgs[i*j] = false;
        }
    }

    flgs
}

fn get_hashed(n: usize) -> usize {
    let mut ret = n;
    while ret > 9 {
        ret = ret.to_string().chars().map(|c| c as usize - '0' as usize).sum::<usize>();
    }
    ret
}

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

    let primes = get_primes(n);
    let primes = (k..=n).filter(|&i| primes[i]).collect::<Vec<usize>>();
    let hashed = primes.iter().map(|&v| get_hashed(v)).collect::<Vec<usize>>();
    let mut maxval = 0usize;
    let mut result = 0usize;
    let mut used = vec![false; 10];
    let mut idx = 0usize;
    let mut cnt = 0usize;
    for i in 0..primes.len() {
        while used[hashed[i]] {
            used[hashed[idx]] = false;
            idx += 1;
            cnt -= 1;
        }
        used[hashed[i]] = true;
        cnt += 1;
        if cnt >= maxval {
            maxval = cnt;
            result = primes[idx];
        }
    }
    println!("{}", result);
}