#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 * pow(10,i) + r;
}

int maxl(int n) {
    if(sieve[n] == -1) return 0;
    int ln = len(n);
    int sum = 1;

    //cout << n << ": " << sieve[n] << "\n";
    if(ln == 1) return sum;


    int child_max = 0;
    for(int i = 0; i < ln; i++) {
        int child = rd(n,i);
        if(sieve[child] != -1) child_max = max(child_max,maxl(child));
    }
    sum += child_max;

    //cout << "maxl " << n << " " << sum << "\n"; 

    return sum;

}

int main(){

    int N;
    cin >> N;

    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 = 2; j <= N / i; j++) {
            sieve[i*j] = -1;
        }
    }

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






}