#![allow(unused_imports)]

use std::io::{self, BufRead};
use std::str::FromStr;
use std::collections::*;
use std::cmp::*;

struct Parser<'a> {
    tokens: &'a mut Iterator<Item = String>,
}

#[allow(dead_code)]
impl<'a> Parser<'a> {
    fn new(i: &'a mut Iterator<Item = String>) -> Self {
        Parser {tokens: i}
    }
    fn take<T: FromStr>(&mut self) -> T {
        match self.tokens.next().expect("empty iterator").parse() {
            Ok(x) => x,
            Err(_) => panic!()
        }
    }

    fn take_some<T: FromStr>(&mut self, n: usize) -> Vec<T> {
        self.tokens.take(n).map(|s| match s.parse() { Ok(x) => x, Err(_) => panic!() } ).collect()
    }
}

//sieve[k] is true if k is a prime
//[0, n)
fn sieve_of_eratosthenes(n: u64) -> Vec<bool> {
    let mut v = vec![true; n as usize];
    v[0] = false;
    v[1] = false;
    for i in 2..n {
        if !v[i as usize] {
            continue;
        }
        let mut j = 2*i;
        while j < n {
            v[j as usize] = false;
            j += i;
        }
    }
    v
}

fn calc_hash(n: u64) -> u8 {
    if n >= 10 {
        let mut t = 0;
        let mut m = n;
        while m > 0 {
            t += m % 10;
            m /= 10;
        }
        calc_hash(t)
    } else {
        n as u8
    }
}

fn main() {
    let stdin = io::stdin();
    let mut tokens = stdin.lock().lines().filter_map(|x| x.ok()).flat_map(|x| x.split_whitespace().map(|s| s.to_owned()).collect::<Vec<String>>());
    let mut parser = Parser::new(&mut tokens);

    let k: u64 = parser.take();
    let n: u64 = parser.take();
    let sieve = sieve_of_eratosthenes(n+1);
    let p: Vec<u64> = sieve.into_iter().zip(0..n+1).filter(|x| x.0).filter(|x| x.1 >= k).map(|x| x.1).collect();
    let mut c = vec![0; 10];
    let mut l = 0;
    let mut u = 0;
    let mut ans_len = 0;
    let mut ans = 0;
    while l < p.len() && u < p.len() + 1 {
        match c.clone().into_iter().max() {
            Some(x) if x >= 2 => {
                c[calc_hash(p[l]) as usize] -= 1;
                l += 1;
            },
            _ => {
                if ans_len <= u-l {
                    ans = p[l];
                    ans_len = u-l;
                }
                if u < p.len() {
                    c[calc_hash(p[u]) as usize] += 1;
                }
                u += 1;
            }
        };
    }
    println!("{}", ans);
}