def prime_sieve(n):
    isprime=[True]*(n+1)
    isprime[0]=False
    isprime[1]=False
    for i in range(2, n+1):
        if isprime[i]:
            for j in range(2*i, n+1, i):
                isprime[j]=False
    return isprime
n=int(input())
a=list(map(int, input().split()))
b=0
for x in a:
    b^=(1<<x)
isprime=prime_sieve(5000000)
def digit(x):
    if not isprime[x]:
        return 0
    b=0
    while x>0:
        b|=(1<<(x%10))
        x//=10
    return b
d=[digit(i) for i in range(5000001)]
pr=0
s=0
ans=-1
for i, x in enumerate(d):
    if (x|b)==b:
        s|=x
        continue
    if s==b:
        ans=max(ans, i-pr-2)
    pr=i
    s=0
if s==b:
    ans=max(ans, 4999999-pr)
print(ans)