void* load(int id) {
    FILE * data_file;
    void* return_data = malloc(40);
    for (unsigned int i = 0; i < indexes[id].file_names.size(); i++) {
        const char* current_filename = indexes[id].file_names[i].c_str();
        int start_reading_position = indexes[id].start_reading_positions[i];
        int end_reading_position = indexes[id].end_reading_positions[i];
        int reading_elements_number = end_reading_position - start_reading_position;
        data_file = fopen(current_filename, "a+b");
        void* current_read_data = (char*) malloc(reading_elements_number);
        fseek(data_file, start_reading_position, 0);
        (void*) fread(current_read_data, 1, reading_elements_number, data_file);
        memcpy(&return_data, &current_read_data, reading_elements_number);
        free (current_read_data);
    }
    return return_data;
}

    void* returned_data = load(1);
    int* casted_data = (int *) &returned_data;
    for (int i = 0; i < array_length; i++) {
        cout << *(casted_data + i) << " ";
    }