#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) (int)(x).size()

bool isprime(int x) {
    if (x <= 1) return false;
    for (int i = 2; i * i <= x; i++) {
        if (x % i == 0) return false;
    }
    return true;
}

int longest(string num) {
    if (num == "") return 0;
    int x = stoi(num);
    num = to_string(x);
    if (!isprime(x)) return 0;
    int ans = 1;
    for (int i = 0; i < sz(num); i++) {
        string res;
        for (int j = 0; j < i; j++) res += num[j];
        for (int j = i+1; j < sz(num); j++) res += num[j];
        ans = max(ans, 1 + longest(res));
    }
    return ans;
}

void solve() {
    string num; cin >> num;
    cout << longest(num) << endl;
}

signed main() {
    solve();
}