import math

a = int(input())

def isPrime(x):
    if x == 1:
        return False
        
    for i in range(2, int(math.sqrt(x))):
        if x % i == 0:
            return False
    else:
        return True

def removeNumber(number):
    if not isPrime(number):
        return 0

    if number < 10:
        return 1

    strNumber = str(number)
    subHighest = 0

    for i in range(len(strNumber)):
        newNumber = int(strNumber[:i] + strNumber[i+1:])
        subHighest = max(subHighest, 1 + removeNumber(newNumber))

    return subHighest

highest = removeNumber(a)

print(highest)