#define _USE_MATH_DEFINES

#include <iostream>	//cin, cout
#include <vector>	//vector
#include <algorithm> //sort,min,max,count
#include <string>	//string,getline, to_string
#include <ios>		//fixed
#include <iomanip>	//setprecision
#include <utility> //swap, pair
#include <cstdlib>	//abs(int)
#include <cmath>	//sqrt,ceil,M_PI, pow, sin
#include <sstream>	//stringstream,getline
#include <numeric>	//gcd, accumlate
#include <deque>	//deque
#include <random>	//randam_device
#include <limits>	//numeric_limits

using namespace std;
constexpr long long int D_MOD = 1000000007;

int main() {

	string N;
	cin >> N;

	if (N.length() == 1) {
		cout << -1 << endl;
		return 0;
	}

	if (N[0] != '1') {
		cout << -1 << endl;
		return 0;
	}

	for (unsigned int i = 1; i < N.length(); i++) {
		if (N[i] != '3') {
			cout << -1 << endl;
			return 0;
		}
	}

	cout << N.length() - 1 << endl;

	return 0;

}