/*
    No.791 うし数列
    https://yukicoder.me/problems/no/791
*/
#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    string n;
    cin >> n;
    if (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;
        }
    }

    cout << (n.size() - 1) << endl;
}