import java.util.HashSet;
import java.util.Scanner;

public class PrayMink {

    static Scanner sc = new Scanner(System.in);

    static HashSet<Integer> primes = new HashSet<>();


    public static void main(String[] args) {

        loadPrimes();

        int num = sc.nextInt();
        System.out.println(search(num, 0));

    }

    public static int search(int num, int length) {
        String numStr = "" + num;
        int max = -1;
        if (isPrime(num)) {
            length = length + 1;
        } else {
            return length;
        }
        for (int i = 0; i < numStr.length(); i++) {
            String nNum = numStr.substring(0, i) + numStr.substring(i + 1);
            if (nNum.isEmpty()) {
                continue;
            }

            int prevMax = search(Integer.parseInt(nNum), length);
            if (prevMax > max) {
                max = prevMax;
            }
        }
        if (length > max) {
            max = length;
        }
        return max;
    }


    public static void loadPrimes() {

        primes.add(2);
        primes.add(3);
        for (int i = 6; i < Math.sqrt(1000000000); i += 6) {
            if (isPrime(i - 1)) {
                primes.add(i - 1);
            }
            if (isPrime(i + 1)) {
                primes.add(i + 1);
            }
        }
    }

    public static boolean isPrime(int num) {
        if (num == 1) {
            return false;
        }
        if (primes.contains(num)) {
            return true;
        }
        for (Integer i : primes) {
            if (num % i == 0) {
                return false;
            }
        }
        return true;
    }

}