import math
from functools import cache

@cache
def isPrime(n):
    if n == 1:
        return False
    last = math.ceil(math.sqrt(n))
    for i in range(2, last):
        if n % i == 0:
            return False
    return True

def func(num, c):
    if len(num) == 0:
        return c

    if not isPrime(int(num)):
        return c
    c += 1
    new_c = c
    for i in range(len(num)):
        temp = ""
        for j in range(len(num)):
            if len(temp) == 0 and num[j] == '0':
                continue
            if j != i:
                temp += num[j]
        new_c = max(new_c, func(temp, c))

    return new_c

data = input()
print(func(data, 0))