def line_ints(): return list(map(int, input().strip().split()))

n = int(input())

def is_primes(p):
    if p < 2:
        return False
    for i in range(2, int(p ** (1/2)) + 2):
        if p % i == 0:
            return False
    return True

max_primes = 0
def backtrack(i, p):
    global max_primes
    max_primes = max(max_primes, i)
    prime = is_primes(p)
    if prime and len(str(p)) > 1:
        for j in range(len(str(p))):
            backtrack(i + 1, int(str(p)[:j] + str(p)[j+1:]))
    if prime:
        backtrack(i + 1, 0)

backtrack(0, n)

print(max_primes)