#include <bits/stdc++.h>

using namespace std;

#define rep(i, a, b) for (int i = a; i < b; i++)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define fo(i, n) rep(i, 0, n)
#define F first
#define S second
#define MP make_pair
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;

ull modmul(ull a, ull b, ull M)
{
	ull ret = a * b - M * ull(1.L / M * a * b);
	return ret + M * (ret < 0) - M * (ret >= (ll)M);
}

ull modpow(ll b, ll e, ll mod)
{
	ull ans = 1;
	for (; e; b = modmul(b, b, mod), e /= 2)
		if (e & 1)
			ans = modmul(ans, b, mod);
	return ans;
}

bool isPrime(ull n)
{
	if (n < 2 || n % 6 % 4 != 1)
		return (n | 1) == 3;
	ull A[] = {2, 325, 9375, 28178, 450775, 9780504, 1795265022},
		s = __builtin_ctzll(n - 1), d = n >> s;

	for (ull a : A)
	{
		ull p = modpow(a % n, d, n), i = s;
		while (p != 1 && p != n - 1 && a % n && i--)
			p = modmul(p, p, n);
		if (p != n - 1 && i != s)
			return 0;
	}
	return 1;
}

constexpr ull tbl[] = {1, 10, 100, 1000, 10'000, 100'000, 1000'000, 10'000'000, 100'000'000, 1000'000'000, 10'000'000'000, 100'000'000'000};

ull digits(ull n)
{
	ull count = 0;

	while (n > 0)
	{
		n /= 10;
		count++;
	}

	return count;
}

ull eat(ull n, ull dig)
{
	return n % tbl[dig] + (n / tbl[dig + 1]) * tbl[dig];
}

unordered_set<ull> visited;

ull calc(ull n) {
	if (visited.find(n) != visited.end())
		return 0;
	visited.insert(n);

	if (!isPrime(n))
		return 0;

	ull digs = digits(n);
	ull best = 0;

	for (ull d = 0; d < digs; d++) {
		ull score = calc(eat(n, d));
		best = max(score, best);
	}

	return best + 1;
}

int main()
{
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(cin.failbit);

	ull orig;
	cin >> orig;

	cout << calc(orig) << endl;
}