#include <iostream>
using namespace std;

int main() {
    string s; cin >> s;
    if (s[0] != '1') { cout << -1; return 0; }
    for (int i = 1; i < s.size(); i++) if (s[i] != '3') { cout << -1; return 0; }
    cout << s.size()-1 << endl;
}