n=int(input())
a=[str(i)[0] for i in input().split()]
maxi=5000000
e=list(range(maxi+1))
e[1]=0
i=2
while i**2<=maxi:
    j=i+i
    while j<=maxi:
        e[j]=0
        j+=i
    i+=1
    while e[i]==0:
        i+=1
list=[]
for i in e:
    if i!=0: list.append(i)

sum_max=0
end_flag=False
def check(num):
    s=str(num)
    for i in range(len(s)):
        if not s[i] in a:
            return False
    return True


l=0
end_list=[0]*n
for r in range(len(list)):
    if check(list[r]):
        for i in range(len(a)):
            for j in range(len(str(list[r]))):
                if a[i]==str(list[r])[j]:
                    end_list[i]=1
        if sum(end_list)==n:
            end_flag=True
            r_index= maxi if r==len(list)-1 else list[r+1]-1
            l_index= 1 if l==0 else list[l-1]+1
            sum_max=max(sum_max,(r_index-l_index))
    else:
        for i in range(len(end_list)): end_list[i]=0
        l=r+1
print(sum_max if end_flag else -1)