#include <iostream>
using namespace std;
int main(void) {
	string s;
	cin >> s;
	int ans = 0;
	for (int i = 1; i < s.size(); ++i) {
		if (s[i] == '3') ++ans;
		else {
			ans = -1;
			break;
		}
	}
	if (s[0] != '1') ans = -1;
	if (s.size() == 1) ans = -1;
	cout << ans << endl;
	return 0;
}