#include <iostream>
#include <string>
#include <iterator>

int main() {
    std::string s;
    std::cin >> s;

    decltype(s)::iterator ite = s.begin();
    char& c = *ite;
    try {
        if (c != '1') throw -1;
        ite++;
        for (; ite != s.end(); ite++) {
            c = *ite;
            if (c != '3') throw -1;
        }
        throw (int) (s.length()-1);
    }
    catch (int e) {
        std::cout << e << std::endl;
    }
}