Problem 44797. Cannibal eating odd and even numbered men

There are N men in a queue. A cannibal eats either all odd-numbered or all even-numbered men in the queue at a time. In the first round he eats all the odd-numbered. In the next round he eats all even-numbered. This goes on repeating (with odd or even toggling after every round) till there is only 1 man in the queue. What would be the original number of this man in the queue? e.g. If N = 6,

Men remaining after round 1: 2, 4, 6

Men remaining after round 2: 2, 6

Men remaining after round 3: 6

Hence answer = 6