Definition: In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.
Input: James T. Kirk:  Let me explain what 's happening here : you are a criminal ! I watched you murder innocent men and women ! I was authorized to * end * you ! And the only reason why you are still alive is because I am allowing it . So * shut your mouth * !
Khan: Captain , are you going to punch me again , over and over , until your arm weakens ... clearly you want to . So tell me , why did you allow me to live ?
James T. Kirk: We all make mistakes .
Khan: I surrendered to you because , despite your attempt to convince me otherwise , you seem to have a conscience , Mr. Kirk . If you did not , then it would be impossible for me to convince you of the truth . 23174611 . Coordinates not far from Earth . If you want to know why I did what I did , go and take a look .
James T. Kirk: Give me one reason why I should listen to you .
Khan: I can give you _ 72 _ . And they 're on board your ship , Captain . They have been , all along .

reason