String operator+(const char lstr, const String& rstr) {
    String copy(1, lstr);
    copy += rstr;
    return copy;
}

String operator+(const String& lstr, const char rstr) {
    String copy = lstr;
    copy.push_back(rstr);
    return copy;
}

String operator+(const String& lstr, const String& rstr) {
    String copy = lstr;
    copy += rstr;
    return copy;
}