The first step to reproducing a flawless batch of Seamus's whiskey awaits on the following page, but you'll need the 2-digit code to access it.

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To achieve the perfect flavor profile Seamus aged his whiskey in four barrels: starting with Bourbon, he then aged in Sherry, Bordeaux, and finished aging his whiskey in a Port barrel for four months. Each barrel's age is half the previous one, except the ex-Bourbon, which is twice the next plus the Port's age.
 

How many months did Seamus age his whiskey in total?