#include <bits/stdc++.h>

using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    string N;
    cin >> N;
    bool flg = true;
    if (N.size() == (unsigned int)(1)) {
        flg = false;
    }
    if (N[0] != '1') {
        flg = false;
    }
    for (unsigned int i = 1; i < N.size(); i++) {
        if (N[i] != '3') {
            flg = false;
        }
    }
    if (flg) {
        cout << N.size() - 1 << endl;
    } else {
        cout << -1 << endl;
    }
    return 0;
}