#include <iostream>
#include <string>
using namespace std;

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