#include <iostream>
#include <regex>
#include <algorithm>
using namespace std;

int main() {
    string N;
    cin >> N;
    regex re("^1(3+)$");
    smatch s;
    if (regex_match(N, s, re)) {
        string ss = s[0];
        cout << count(ss.begin(), ss.end(), '3') << endl;
    } else {
        cout << "-1" << endl;
    }
    return 0;
}