#include <iostream>
#include <algorithm>
#include <string>

using namespace std;

bool isPrime(string num)
{
	if (num == "")
	{
		return false;
	}
	int x = stoi(num);
	if (x == 1)
	{
		return false;
	}
	for (size_t i = 2; i <= sqrt(x); i++)
	{
		if (x % i == 0)
		{
			return false;
		}
	}
	return true;
}

void fun(string num, int& max, int curr) {
	while (num.length() > 0 && num[0] == '0')
	{
		num.erase(0,1);
	}
	if (isPrime(num))
	{
		++curr;
	}
	else
	{
		return;
	}
	max = std::max(max, curr);

	for (size_t i = 0; i < num.length(); i++)
	{
		string pom = num;
		pom.erase(i, 1);
		fun(pom, max, curr);
	}
}

int main()
{
    int x;
    cin >> x;
	int max = 0;

	string s = to_string(x);
	fun(s, max, 0);
	cout << max;
}