#include <iostream>

using namespace std;

int main() {
    string s;
    cin >> s;

    bool ok = s[0] == '1' && s.size() > 1;
    for (int i = 1; i < s.size(); i++) {
        if (s[i] != '3')ok = false;
    }

    cout << (ok ? (int) s.size() - 1 : -1) << endl;
    return 0;
}