Balanced Fence Partition

Farmer John's $N$ cows each stand at a distinct location $(x_1, y_1), \ldots, (x_N, y_N)$ on his two-dimensional farm. Every coordinate $x_i$ and $y_i$ is a positive odd integer no larger than $B$.

John wants to split the farm with a north-south fence of effectively infinite length, given by the equation $x = a$. The value $a$ is even, so the fence never runs through the spot where a cow stands. He also builds an east-west fence of effectively infinite length given by $y = b$, where $b$ is even as well. The two fences cross at the point $(a, b)$ and cut the farm into four regions.

John wants the cows spread evenly over the four regions, with no single region holding too many of them. Let $M$ be the number of cows in the most crowded of the four regions. Find the smallest value of $M$ he can reach.

The first line contains two integers $N$ and $B$ ($1 \leq N \leq 100$, $1 \leq B \leq 10^6$), separated by a space. Each of the next $N$ lines contains the $x$ coordinate and the $y$ coordinate of one cow. Every coordinate is a positive odd integer no larger than $B$, and no two cows share a location.

Print on one line the smallest value of $M$ that John can reach by placing the two fences optimally.