def cache(f):
    answers = {}
    def cached(n):
        if not n in answers: answers[n] = f(n)
        return answers[n]
    return cached

@cache
def solve(n):
    if n < 10:
        return 1 if is_prime(n) else 0
    s = str(n)
    if not is_prime(n):
        return 0
    best = 0
    for i in range(len(s)):
        new_s = s[:i] + s[i + 1:]
        current = solve(int(new_s))
        best = max(best, current)
    return best + 1

def is_prime(n):
    if n < 2: return False
    for d in range(2, int(n ** 0.5) + 1):
        if n % d == 0: return False
    return True

print(solve(int(input())))