#include <bits/stdc++.h>

using namespace std;

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