import math
N=int(raw_input())
A=set(raw_input().split())

upperBound = 5000001
isPrime=[True for i in range((upperBound-3)/2+1)]
for i in range((int(math.sqrt(upperBound-3))-3)/2+1): # k*k = (2i+3)^2 <= upperBound-3 
   if isPrime[i]:
      k = i+i+3 # this is prime number
      # false out non_prime number from k*k
      # k*k = 4i^2+12i+9 = 2*(2i^2+6i+3)+3
      # k*(k+1) = 2*(2i^2+6i+3)+3 + 2i+3 ... even number. skip
      # k*(k+2) = 2*(2i^2+6i+3+k)+3 
      non_prime = k*(i+1)+i
      for j in range(non_prime,(upperBound-3)/2+1,k):
         isPrime[j]=False
primes = [2] + [i+i+3 for i in range((upperBound-3)/2+1) if isPrime[i]==True]
#print len(primes)
ans = -1
start = 1
cnt = 0
S=set()
for i in primes:
   tmpS = set(str(i))
   if len(tmpS-A) >0:
      if cnt > 0 and len(S)==len(A):
         ans = max(ans, i-1-start)
      start = i+1
      cnt = 0
      S=set()
   else:
      S=S.union(set(str(i)))
      cnt+=1
if cnt > 0 and len(S)== len(A) :
   ans = max(ans,5000000-start)
print ans