How to display all the values in auto drop down list using selenium web driver when it is developed using tag

How to display all the values in auto drop down list using selenium web driver when it is developed using tag.

My code

driver.get("https://www.yatra.com/");// URl of yatra
    String origin ="(//input[@name='flight_origin_city'])[1]";// text box for entering origin
    driver.findElement(By.xpath(origin)).sendKeys("Bangalore");
    String destination = "(//input[@name='flight_destination_city'])[1]";// text for entering destination
    driver.findElement(By.xpath(destination)).sendKeys("M");
    List<WebElement> lists= driver.findElements(By.xpath("(//div[@class='viewport'])[2]")); // this is the div where all the values are present .

    for (int i=0; i<lists.size();++i){

        System.out.println(lists.get(i).getText());// getting the text for all the values.
    }