from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline
M = 5*10**6
class prime_factorize():
    
    def __init__(self,M=10**6):
        self.sieve = [-1]*(M+1)
        self.sieve[1] = 1
        self.p = [False]*(M+1)
        self.mu = [1]*(M+1)
        
        for i in range(2,M+1):
            if self.sieve[i] == -1:
                self.p[i] = True
                
                i2 = i**2
                for j in range(i2,M+1,i2):
                    
                    self.mu[j] = 0
                
                
                for j in range(i,M+1,i):
                    self.sieve[j] = i
                    
                    self.mu[j] *= -1
                    
    def factors(self,x):
        tmp = []
        while self.sieve[x] != x:
            tmp.append(self.sieve[x])
            x //= self.sieve[x]
        tmp.append(self.sieve[x])
        return tmp
        
    def is_prime(self,x):
        return self.p[x]
        
    def mobius(self,x):
        return self.mu[x]
        
pf = prime_factorize(M)
primes = []
for i in range(2,M+1):
    if pf.is_prime(i):
        primes.append(i)

N = int(input())
A = list(map(int,input().split()))
B = []
for i in range(10):
    if i in A:
        continue
    B.append(i)
A = set(A)
B = set(B)

ans = -1
S = set()
l=0
r=0
n = len(primes)
while r<n:
    
    for j in str(primes[r]):
        S.add(int(j))

    
    if len(S&B)!=0:
        l = r+1
        r = l
        S = set()
        continue
    if S&A==A:
        if r==n-1:
            if l==0:
                ans = max(ans,M-1)
            else:
                ans = max(ans,M - primes[l-1]-1)
        else:
            if l==0:
                ans = max(ans,primes[r+1]-1-1)
            else:
                ans = max(ans,primes[r+1]-1 - (primes[l-1]+1))
                
    
    r += 1
print(ans)