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

int count_string(string n) {
    int cnt = 0;
    for (auto ch : n)
        if (ch == '3')
            cnt++;
    return cnt;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    string n;
    cin >> n;
    if (n[0] != '1' || n.size() == 1) {
        cout << -1 << endl;
        return 0;
    }

    int cnt = count_string(n);
    if (cnt == (int)n.size() - 1) {
        cout << cnt << endl;
    } else {
        cout << -1 << endl;
    }
}