Coin Game

Abhishek and Sudhanshu were bored and decided to play a game. They only had some coins so they arranged all the '$N$' coins in a straight line with random face up(heads or tails). Abhishek asked Sudhanshu to flip coins in such a manner that all heads faces are up. But he also restricted the method of flipping as ,"If u flip a coin at '$k$'th position, then all the coins after '$k$' must also be f