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

    // find prime k ~ n
    let mut prime: Vec<bool> = vec![true; n + 1];
    let mut i: usize = 2;
    prime[1] = false;
    while i * i <= n {
        if prime[i] {
            let mut j: usize = i * 2;
            while j <= n {
                prime[j] = false;
                j += i;
            }
        }
        i += 1;
    }
    let target: Vec<usize> = (k..n + 1).filter(|&i| prime[i]).collect();

    // search
    let mut l: usize = 0;
    let mut r: usize = 0;
    let mut ans: usize = 0;
    let mut max: usize = 0;
    let mut cnt: Vec<u32> = vec![0; 10];
    while l < target.len() {
        while r < target.len() && cnt[target[r] % 9] == 0 {
            cnt[target[r] % 9] += 1;
            r += 1;
        }
        if r - l >= max {
            max = r - l;
            ans = target[l];
        }
        if r == l {
            r += 1;
        }

        cnt[target[l] % 9] -= 1;
        l += 1;
    }
    println!("{}", ans);
}