def isPrime(number):
    if number == 0 or number == 1:
        return False
    arr = [i for i in range(2, number+1)]
    count = 0
    for item in arr:
        if number%item==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):
    counter = 0
    first_try = True
    while number>0:
        if first_try and not isPrime(number):
            first_try = False
            if number_length(number) == 1:
                break
            else:
                number = number%(10*(number_length(number)-1))
        elif isPrime(number):
            counter = counter+1
            if number_length(number) == 1:
                break
            else:
                number = number%(10*(number_length(number)-1))
        else:
            break
    return counter


if __name__ == '__main__':
    number = int(input())
    print(count_primes(number))