A large discount store gives its sales personnel bonuses based on their average sale amount. Since each salesperson makes hundreds of sales each month, the store management decided to base average sale amount for each salesperson on a random sample of the person's sales. Since records of sales are kept in books, the use of systematic sampling is convenient. Suppose a salesperson has made 855 sales over the month, and management wants to choose a sample of 30 sales for estimation of the average amount of all sales. Suggest a way of doing this so that no problems would result due to the fact that 855 is not an integer multiple of 30. Give the first element you choose to select, and explain how the rest of the sample is obtained.