Definition: Generate a correct and concise answer for the question based on the words in the context.

Positive Example 1 -
Input: Context : Isaac Nicola Romero (1916 in Havana, Cuba -- 1997) was a prominent Cuban guitarist and one of the founders of the modern Cuban Guitar School. 
Question : What was Isaac Nicola's city of birth?
Output: Havana

Positive Example 2 -
Input: Context : Tweetie Pie won the Academy Award for Best Animated Short Film, breaking Tom and Jerry's streak of four consecutive wins on the category. 
Question : What award was Tweetie Pie nominated for?
Output: Academy Award for Best Animated Short Film

Negative Example 1 -
Input: Context : An Officer and a Gentleman is a 1982 American drama/romance film that stars Richard Gere, Debra Winger and Louis Gossett, Jr., who won the Academy Award for Best Supporting Actor for the film, and was produced by Lorimar Productions for Paramount Pictures. 
Question : What award was An Officer and a Gentleman nominated for?
Output: 1982

Negative Example 2 -
Input: Context : Travis Hamonic (born August 16, 1990) is a Canadian professional ice hockey defenseman currently playing for the New York Islanders of the National Hockey League (NHL). 
Question : What team does Travis Hamonic belong to?
Output: Boston Bruins

Now complete the following example -
Input: Context : In cryptography, DES-X (or DESX) is a variant on the DES (Data Encryption Standard) symmetric-key block cipher intended to increase the complexity of a brute force attack using a technique called key whitening. 
Question : Which is the basis of DES-X?
Output: Data Encryption Standard