def eratosthenes(n):
    primes=set(range(2,n+1))
    for i in range(2,n):
        if i in primes:
            it = i ** 2
            while it <= n:
                if it in primes:
                    primes.remove(it)
                it += i
    return primes

P=sorted(list(eratosthenes(5*10**6)))

n=int(input())
A=list(map(int,input().split()))

digit = [0 for _ in range(10)]
for a in A:
    digit[a]=1

ans=-1
n_digit = [0 for _ in range(10)]

P.append(5*10**6+1)
k=1
for i in range(len(P)-1):
    p=P[i]
    while(p>0):
        n_digit[p%10]=1
        p//=10
    
    flag=1
    for j in range(10):
        if digit[j]==0 and n_digit[j]==1:
            for l in range(10):
                n_digit[l]=0
            k=P[i]+1
            flag=0
            break
        if digit[j]==1 and n_digit[j]==0:
            flag=0
    if flag==1:
        ans=max(ans,P[i+1]-1-k)

print(ans)