maxx = 10000000

def mkp(x):
  P = [2]
  p = [2]
  n = 3
  while n < x:
    for i in p:
      if n % i == 0:
        break
    else:
      P.append(n)
    n += 2
    while n > p[-1] ** 2:
      p.append(P[len(p)])
  return P

prime = mkp(2 * maxx ** 0.5)

p = maxx ** 0.5
pi = 0
for i in xrange(len(prime)):
  if prime[i] > p:
    pi = i
    break
q = maxx / p
qi = 0

nn, dndn = 0, 1

while pi > 1:
  pi -= 1
  p = prime[pi]
  q = maxx / p
  for i in xrange(len(prime) - 1, pi, -1):
    if prime[i] < q:
      qi = i + 1
      break
  while qi > pi:
    qi -= 1
    q = prime[qi]
    n = p * q
    if n > maxx:
      continue
    dn = p + q - 1
    if n * dndn > nn * dn:
      sn = str(n)
      sdn = str(n - dn)
      if sorted(sn) == sorted(sdn):
        nn = n
        dndn = dn
        break

print nn