import sys
input=lambda: sys.stdin.readline().rstrip()
n=int(input())
A=set(int(i) for i in input().split())
def primes(n):
  is_prime=[True]*(n+1)
  is_prime[0]=False
  is_prime[1]=False
  for i in range(2,int(n**0.5)+1):
    if not is_prime[i]:
      continue
    for j in range(i*2,n+1,i):
      is_prime[j]=False
  return [i for i in range(n+1) if is_prime[i]]
P=primes(5*10**6)
cur=set()
prev=1
ans=0
for i,p in enumerate(P):
  cur2=set()
  chk=True
  for pp in str(p):
    if int(pp) in A:
      cur2.add(int(pp))
    else:
      chk=False
      break
  if chk:
    for c in cur2:
      cur.add(c)
  else:
    if A==cur:
      ans=max(ans,p-prev-1)
    cur=set()
    prev=p+1
if A==cur:
  ans=max(ans,5*10**6-prev)
print(ans)