I need help with a word problem please. King Arthur has 27 knights sitting at his table. In order to select one to marry his daughter he will go around the table telling the first one to stay, the second one to leave, the third to stay, the fourth to leave. He will continue to go around and around until only one is left. Which knight is left? How would one create a method to know which seat to sit in, no matter how many knights are at the table?

I understand the first question, it is the 23rd knight. But I don't know how to develop a method.

Question

I need help with a word problem please. King Arthur has 27 knights sitting at his table. In order to select one to marry his daughter he will go around the table telling the first one to stay, the second one to leave, the third to stay, the fourth to leave. He will continue to go around and around until only one is left. Which knight is left? How would one create a method to know which seat to sit in, no matter how many knights are at the table? 

I understand the first question, it is the 23rd knight. But I don't know how to develop a method.