from functools import lru_cache

@lru_cache(10)
def is_prime(n):
    if n == 1:
        return False
    for x in range(2, n // 2 + 1):
        if n % x == 0:
            return False
    else:
        return True

# print(is_prime(300_007))
line = input()
chars = list(line)
length = len(line)
count = 0

while len(chars) != 0:
    if len(chars) > 0 and chars[0] == "0":
        for _ in range(length):
            if chars[0] != "0":
                break
            chars.pop(0)
    if not is_prime(int("".join(chars))):
        break

    chars.pop(0)
    count += 1

print(count)