King Arthur IMP3 Math POW help! How?

King Arthur had Knights at round table.The King had Knights play a game. 1st King Arthur put #s on chairs, beginning w/ 1 & continuing around table, w/ 1 chair for each Knight. Every chair was occupied, King A. remained standing. King A. stood behind the Knight in chair #1 & said you're in.Next he moved to Knight in chair 2 & said you're out .And that Knight left his seat.Next he moved to Knight in chair 3 & said you're in, then out to Knight in chair 4. that Knight left game. King A. continued around table in this manner & came back to Knight in chair 1, either you're in or out depending on what he had said to previous Knight. King A. kept moving around table alternately saying you're in or out to each Knight. If chair was empty, he skipped it; he continued until only 1 Knight was left sitting at table, that Knight was the winner. The # of Knights vary from day to day.If you knew how many Knights were going to be at the table, how could you determine which chair would win? CONT..