Expected move

You are given a fair coin and two integers $X$ and $N$. You repeatedly flip the coin and perform the following operation based on the result: - If it lands on heads, then $X$ will **increase** by $1$. However, if $X = N$ then $X$ will **not** change. - If it lands on tails, $X$ will **decrease** by $1$. You stop as soon as the value of $X$ becomes $1$. Find the expected number of coin flips. N