Problem:
Score : 500 points

Problem Statement

AtCoDeer is thinking of painting an infinite two-dimensional grid in a checked pattern of side K.
Here, a checked pattern of side K is a pattern where each square is painted black or white so that each connected component of each color is a K × K square.
Below is an example of a checked pattern of side 3:

AtCoDeer has N desires.
The i-th desire is represented by x_i, y_i and c_i.
If c_i is B, it means that he wants to paint the square (x_i,y_i) black; if c_i is W, he wants to paint the square (x_i,y_i) white.
At most how many desires can he satisfy at the same time?

Constraints

1 ≤ N ≤ 10^5

1 ≤ K ≤ 1000

0 ≤ x_i ≤ 10^9

0 ≤ y_i ≤ 10^9

If i ≠ j, then (x_i,y_i) ≠ (x_j,y_j).

c_i is B or W.

N, K, x_i and y_i are integers.

Input

Input is given from Standard Input in the following format:

N K
x_1 y_1 c_1
x_2 y_2 c_2
:
x_N y_N c_N

Output

Print the maximum number of desires that can be satisfied at the same time.

Sample Input 1

4 3
0 1 W
1 2 W
5 3 B
5 4 B

Sample Output 1

4

He can satisfy all his desires by painting as shown in the example above.

Sample Input 2

2 1000
0 0 B
0 1 W

Sample Output 2

2

Sample Input 3

6 2
1 2 B
2 1 W
2 2 B
1 0 B
0 6 W
4 5 W

Sample Output 3

4

Solution in Python (3.4.3) (judge verdict: Accepted)

import sys
import numpy as np
from collections import Counter

read = sys.stdin

N, K = map(int, read.readline().split())
k = 2 * K
xyc = np.array(read.read().split(), np.str).reshape(-1, 3)
x = xyc[:, 0].astype(int)
y = xyc[:, 1].astype(int)
c = xyc[:, 2]

x[c == 'B'] -= K
x %= k
y %= k

grid = np.zeros((3 * K, 3 * K), np.int64)
np.add.at(grid, (x, y), 1)
np.add.at(grid, (x + K, y + K), 1)
np.subtract.at(grid, (x + K, y), 1)
np.subtract.at(grid, (x, y + K), 1)
np.cumsum(grid, axis=0, out=grid)
np.cumsum(grid, axis=1, out=grid)

p1 = grid[:K, :K] + grid[k:, k:] + grid[K:k, K:k] + grid[k:, :K] + grid[:K, k:]
p2 = grid[K:k, :K] + grid[K:k, k:] + grid[:K, K:k] + grid[k:, K:k]
print(max(p1.max(), p2.max()))