#include <iostream>
#include <vector>
#include <cmath>
using namespace std;

vector<int> sieve;


int len(int n) {
    if(n == 0) return 0;
    return floor(log10(n)) + 1;
}

int rd(int n, int i) {
    int l = n / int(pow(10,i+1));
    int r = n % int(pow(10,i));
    return l * int(pow(10,i)) + r;
}


bool is_prime(int n) {
    if(n < 2) return false;
    for(int i = 2; i <= floor(sqrt(n)); i++) {
        if(n % i == 0) return false;
    }


    return true;

}



int maxl(int n) {
    int ln = len(n);

    int sum = 1;
    if(!is_prime(n)) return 0;
    if(ln == 1) return 1;


    int child_max = 0;
    for(int i = 0; i < ln; i++) {
        int child = rd(n,i);
        if(is_prime(child)) child_max = max(child_max, maxl(child));
    }
    sum += child_max;
    return sum;

}

int main(){
    int N;
    cin >> N;

    cout << maxl(N) << "\n";

    return 0;

    sieve.push_back(-1);
    sieve.push_back(-1);
    for(int i = 2; i <= N; i++) sieve.push_back(i);
    for(int i = 2; i <= N; i++) {
        if(sieve[i] == -1) continue;
        for(int j = i*2; j <= N; j += i) {
            sieve[j] = -1;
        }
    }

    cout << maxl(N) << "\n";






}