String operator+(const String& left, const String& right) {
    cout << "length " << left.length() + right.length() << endl;
    char* sum = new char[left.length() + right.length() + 1];
    int i_sum = 0;
    for (int i = 0; left.string[i] != '\0'; i++, i_sum++) {
        sum[i_sum] = left.string[i];
    }
    for (int i = 0; right.string[i] != '\0'; i++, i_sum++) {
        sum[i_sum] = right.string[i];
    }
    cout << i_sum << endl;
    sum[i_sum] = '\0';
    String result = sum;
    delete[] sum;
    return result;
}