One-XOR Deletions

Chef has with him an array $A$ of length $N$. In one move, he can delete any element from $A$. Find the minimum number of deletions Chef must make so that the following condition holds: - Let $B$ denote the resulting array, and $M$ be the length of $B$. - Then, $B_i \oplus B_j \leq 1$ for every $1 \leq i, j \leq M$. Here, $\oplus$ denotes the [bitwise XOR](https://en.wikipedia.org/wiki/Bitwise_o