#include <fstream>
#include <iostream>


int main() {

	//std::ifstream inf("Text.txt");	std::cin.rdbuf(inf.rdbuf());

	int N;
	std::cin >> N;

	int ans = 0;
	while (1) {
		if (N == 1) {
			break;
		}
		if (N % 10 == 3) {
			ans++;
			N = N / 10;
		}
		else{
			ans = -1;
			break;
		}
	}

	std::cout << ans << std::endl;

	return 0;

}