#include <bits/stdc++.h>
using namespace std;

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