import sequtils,strutils,strscans,algorithm,math,future,sets,queues,tables,macros
macro unpack*(rhs: seq,cnt: static[int]): auto =
  let t = genSym(); result = quote do:(let `t` = `rhs`;())
  for i in 0..<cnt: result[0][1].add(quote do:`t`[`i`])
template get*():string = stdin.readLine()
template times*(n:int,body:untyped): untyped = (for _ in 0..<n: body)
template `max=`*(x,y:typed):void = x = max(x,y)
template `min=`*(x,y:typed):void = x = min(x,y)

proc `+=`[T](x:var set[T],y:T):void = x.incl(y)
proc `-=`[T](x:var set[T],y:T):void = x.excl(y)
proc `+=`[T](x:var set[T],y:set[T]):void = x = x.union(y)
proc `*=`[T](x:var set[T],y:set[T]):void = x = x.intersection(y)
proc `-=`[T](x:var set[T],y:set[T]):void = x = x.difference(y)
converter toInt8(x:int) : int8 = x.toU8()

proc parseDecimal(n:int) : auto = ($n).mapIt(it.ord - '0'.ord)
proc getIsPrimes(n:int) :seq[bool] = # [0...n]
  result = newSeqWith(n+1,true)
  result[0] = false
  result[1] = false
  for i in 2..n.float.sqrt.int :
    if not result[i]: continue
    for j in countup(i*2,n,i):
      result[j] = false

proc getPrimes(n:int,start:int = 0):seq[int] = # [2,3,5,...n]
  let isPrime = getIsPrimes(n)
  result = @[]
  for i,p in isPrime:
    if i < start: continue
    if p : result &= i

proc hash(n:int) : int =
  result = ($n).mapIt(it.ord - '0'.ord).sum()
  if result > 9:
    result = hash(result)

let
  K = get().parseInt
  N = get().parseInt
  primes = getPrimes(N,start=K)

if false: # 愚直な実装
  var
    L = 0
    hashes : set[int8] = {}
    ans = (prime:0, card:0)
  for p in primes:
    let h = hash(p)
    if h in hashes:
      while h in hashes:
        hashes -= hash(primes[L])
        L += 1
    hashes += h
    if hashes.card >= ans.card:
      ans.prime = primes[L]
      ans.card = hashes.card
  echo ans.prime

else: # 最適化
  # hash は 0,3,6,9にならない (3は一度だけ) => 124578の6が最大だが、大きい方を優先するので大きい方から回す
  if K <= 3:
    if N <= 3:# 12 13 23
      if K == 1: echo N
      else: echo 3
    else:
      if N < 11: echo 2
      else: echo 3
    quit()

  var
    L = 0
    hashes : set[int8] = {}
    ans = (prime:0, card:0)
  let primeHashReverseds = primes.mapIt(it.hash()).reversed()
  for i,h in primeHashReverseds:
    if h in hashes:
      while h in hashes:
        hashes -= primeHashReverseds[L] #hash(primes[R])
        L += 1
    hashes += h
    if hashes.card >= ans.card:
      ans.prime = primes[^(i+1)]
      ans.card = hashes.card
      if ans.card == 6: break
  echo ans.prime