import strutils,sequtils,algorithm

proc CToI(c : char):int =
    return int(c) - int('0')

var
    K = stdin.readline.parseInt
    N = stdin.readline.parseInt
    sosuu = newSeq[int](0)
    natu = newSeqWith(N + 1,true)
    k : int

for i in 2..N:
    if natu[i]:
        k = i
        while k <= N:
            natu[k] = false
            k += i
        sosuu.add(i)

var
    Nid,Kid : int
    H : seq[int]
    s : string
    flag = newSeqWith(10,false)
    rig,lef,ans,M : int

Nid = sosuu.lowerBound(N) - 1
Kid = sosuu.lowerBound(K)
if sosuu[^1] == N:
    Nid += 1


H = @[]
for i in sosuu[Kid..Nid]:
    k = i
    while k >= 10:
        s = $k
        k = 0
        for t in s:
            k += CToI(t)
    H.add(k)
lef = 0

M = 0
for rig in 0..H.high:
    if flag[H[rig]] == false:
        flag[H[rig]] = true
    else:
        while flag[H[rig]] == true:
            flag[H[lef]] = false
            lef += 1
        flag[H[rig]] = true
        
    if rig - lef + 1 >= M:
        ans = sosuu[Kid + lef]
        M = rig - lef + 1
    if M == 7:
        break
echo ans