import std.algorithm, std.array, std.container, std.range, std.bitmanip;
import std.numeric, std.math, std.bigint, std.random;
import std.string, std.conv, std.stdio, std.typecons;

void main()
{
  auto k = readln.chomp.to!int;
  auto n = readln.chomp.to!int;

  auto pi = primes(n).assumeSorted.upperBound(k - 1).array;
  auto hi = pi.map!(calcHash).array;

  auto memo = new int[](10);
  memo[] = -1;

  auto maxLen = 0, maxPos = 0;
  auto s = 0, i = 0;
  while (i < hi.length) {
    auto h = hi[i];

    if (memo[h] < 0) {
      memo[h] = i;
      i += 1;
    } else {
      auto len = i - s;
      if (len >= maxLen) {
        maxLen = len;
        maxPos = s;
      }
      s = i = memo[h] + 1;
      memo[] = -1;
    }
  }
  auto len = i - s;
  if (len >= maxLen) {
    maxLen = len;
    maxPos = s;
  }

  writeln(pi[maxPos]);
}

int calcHash(int n)
{
  auto r = 0;
  while (n > 0) {
    r += n % 10;
    n /= 10;
  }
  if (r < 10)
    return r;
  else
    return calcHash(r);
}

int[] primes(int n)
{
  auto sieve = new bool[](n + 1);
  sieve[0..2] = false;
  sieve[2..$] = true;

  foreach (p; 2..n.to!real.sqrt.to!int + 1)
    if (sieve[p])
      foreach (q; iota(p * 2, n + 1, p))
        sieve[q] = false;

  return sieve.enumerate
    .filter!("a[1]")
    .map!("a[0]").map!(to!int).array;
}