#include <bits/stdc++.h>

using namespace std;

#define For(i, a, n) for(int i =a;i<n;i++)
#define endl '\n'
#define vec vector

typedef long long ll;
typedef pair<ll, ll> pii;
template<typename... Args>
void dbg(Args&&... args){
    ((cerr<<args<<" |"),...);
    cerr<<endl;
}
template<class A, class B>
pair<A, B> operator+(const pair<A, B>&a, const pair<A, B>& b){
    return {a.first +b.first, a.second + b.second};
}
template<class A, class B>
ostream& operator<< (ostream& os, const pair<A, B>& a){
    return os<<"("<<a.first<<", "<<a.second<<")";
}
template<class A, class B, class C>
basic_ostream<A, B>& operator<<(basic_ostream<A, B>& os, const C&c){
    for(auto it=begin(c); it!=end(c);++it){
        os<<(it==begin(c)?"":" ")<<*it;
    }
    return os;
}

map<int, int> memo;

bool is_prime(int n){
    if(n<=1)return false;
    For(i, 2, sqrt(n)+1){
        if(n%i==0)return false;
    }
    return true;
}

int f(int n){
    if(n == 0)return 0;
    if(memo.count(n))return memo[n];
    int t =0;
    string s = to_string(n);
    if(!is_prime(n))return memo[n] = 0;
    // dbg("n is prime", n);
    For(i, 0, s.size()){
        string ns = "0";
        For(j, 0, s.size()){
            if(j!=i)ns+=s[j];
        }
        t = max(t, f(stoi(ns)));
    }
    return memo[n] = 1+ t;
}


void solve(){
    int n;cin>>n;
    cout<<f(n)<<endl;
}

main(){
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    int t=1;//cin>>t;
    while(t--){
        solve();
    }
}