#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
signed main() {
	ios::sync_with_stdio(false); cin.tie(0);
	string s;
	cin >> s;
	if (s[0] != '1') {
		cout << -1 << endl;
		return 0;
	}
	if ((int) s.length() == 1) {
		cout << -1 << endl;
		return 0;
	}
	for (int i = 2; i < (int) s.length(); i++) {
		if (s[i] != '3') {
			cout << -1 << endl;
			return 0;
		}
	}
	cout << (int) s.length() - 1 << endl;
	return 0;	
}