#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using ld = long double;
#define print(x) cerr << #x << " = " << x << endl

unordered_map<int, int> seen;

template<class T>
ostream& operator<<(ostream &out, vector<T> &cont) {
    out << "[";
    for (const auto &x : cont) out << x << ", ";
    out << "]";
    return out;
}

bool isPrime(int n){
    if(n < 2)
        return false;

    if (n % 2 == 0) return false; 
    for(int i=3; i*i<=n; i += 2){
        if(n%i == 0)
            return false;
    }
    return true;
}


int solve(int n){
    if(n == 0 || !isPrime(n))
        return 0;

    if (seen.find(n) != seen.end()){
        return seen[n];
    }

    int n2 = n, i = 1;
    vector<int> a;
    while(n2 != 0){
        a.push_back(i*(n2%10));
        i *= 10;
        n2 /= 10;
    }

    int maxAns = 0;
    for(int i=0; i<a.size(); i++){
        int newN = n;
        newN -= a[i];
        for(int sub=i+1; sub<a.size(); sub++){
            newN += -a[sub] + a[sub]/10;
        }
        
        maxAns = max(maxAns, solve(newN));
    }
    
    seen[n] = 1 + maxAns;
    //cout << n << ' ' << currAns << ' ' << maxAns << '\n';
    return 1 + maxAns;
}

int32_t main() {
    int n;
    cin >> n;

    cout << solve(n) << '\n';

}