from copy import copy
from math import *

def is_prime(num):
    for i in range(2, ceil(sqrt(num)) + 1):
    # for i in range(2, num):
        if num % i == 0:
            return False
    return True

def r(n, res):
    s = [i for i in str(n)]
    if len(s) <= 1:
        return res
    arr = []
    for i in range(len(s)):
        s_copy = copy(s)
        s_copy.pop(i)
        num = int(''.join(s_copy))
        if is_prime(num):
            arr.append(num)
    new_res = res + 1
    for i in range(len(arr)):
        new_res = max(new_res, r(arr[i], res + 1))
    return new_res


N = int(input())
print(r(N, is_prime(N)))