arr = []
def is_prime(number):
    global arr
    arr = [i for i in range(number + 2)]
    arr[1] = 0
    i = 2
    while i <= number:
        if arr[i]:
            j = i + i
            while j <= number:
                arr[j] = 0
                j += i
        i += 1
    return arr[number]

    # if number == 0 or number == 1:
    #     return False
    # count = 0
    # for i in range(2, number + 1):
    #     if number % i == 0:
    #         count = count+1
    #     if count > 1:
    #         return False
    # return True




def number_length(number):
    lengt = 0
    while number>0:
        number = number//10
        lengt = lengt+1
    return lengt

def count_primes(number):
    counter1 = 0
    counter2 = 0
    while number>0:
        if is_prime(number):
            counter1 = counter1+1
            if number_length(number) == 1:
                break
            else:
                number = number%(10**(number_length(number)-1))
        else:
            break
    while number>0:
        if is_prime(number):
            counter2 = counter2+1
            if number_length(number) == 1:
                break
            else:
                number = number//10
        else:
            break


    return max(counter1, counter2)
# max_count = 0
#
# def rec(number, count):
#
#     global max_count
#     if arr[number]:
#         count += 1
#     else:
#         return
#     # print(number, count)
#     max_count = max(max_count, count)
#     if number_length(number) == 1:
#         return
#     rec(number % pow(10, (number_length(number)-1)), count)
#     rec(number // 10, count)




if __name__ == '__main__':
    number = int(input())
    is_prime(number)
    # rec(number, 0)
    # print(max_count)
    print(count_primes(number))