#include <algorithm>
#include <iostream>
#include <iomanip>
#include <cstring>
#include <string>
#include <vector>
#include <queue>
#include <cmath>
#include <stack>
#include <set>
#include <map>
typedef long long ll;
typedef unsigned int uint;
using namespace std;

int main() {
	string N;
	cin >> N;
	int ans = 0;

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

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