table = {}

def check_prime(m):
    if m == 1:
        return 0
    for i in range(2,m):
        if m % i == 0:
            return 0
    return 1

def dfs(n):
    if n in table:
        return table[n]
    if check_prime(n) == 0:
        return 0
    if n<10:
        return 1
    dup = str(n)
    summ = 0
    for i in range(len(dup)):
        new_n = int(dup[:i]+dup[i+1:])
        summ = max(summ, dfs(new_n))
    table[n] = summ
    return summ+1

n = int(input())

"""
is_prime = [1 for i in range(n+1)]
is_prime[0] = 0
is_prime[1] = 0
for i in range(2, int(n**0.5)+1):
    if is_prime[i] == 0:
        continue
    neww = i*2
    while neww < int(n+1):
        is_prime[neww] = 0
        neww += i
"""


print(dfs(n))