k = int(input())
n = int(input())
siv = [True]*(n+1)
siv[0] = siv[1] = False
for i in range(2, int(n**0.5)+2):
    if not siv[i]:
        continue
    for j in range(i*2, n+1, i):
        siv[j] = False
prm = [i for i in range(k, n+1) if siv[i]]
def hsh(x):
    x = sum(map(int, str(x)))
    if x >= 10:
        return hsh(x)
    return x
vis = set()
mx = res = beg = 0
end = -1
while end < len(prm)-1:
    h = hsh(prm[end+1])
    if h in vis:
        vis.remove(hsh(prm[beg]))
        beg += 1
    else:
        vis.add(h)
        end += 1
        if len(vis) >= mx:
            mx = len(vis)
            res = prm[beg]
print(res)