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: Runtime Error)

#!/usr/bin/env python3
# coding=utf-8

import itertools
import sys

import numpy as np

n, k = map(int, sys.stdin.readline().strip().split(" "))
xyc = [l.strip().split(" ") for l in sys.stdin.readlines()]
xy = [tuple((int(_x), int(_y) if _c == "W" else int(_y) + k)) for (_x, _y, _c) in xyc]
xy = [tuple((_x % (2 * k), _y % (2 * k))) for (_x, _y) in xy]

check = np.zeros((n, 2*k, 2*k))
for _i, (_x, _y) in enumerate(xy):
    for _j, _k in itertools.product(range(2*k), range(2*k)):
        check[_i, _j, _k] = 1 if ((_j - _x) // k + (_k - _y) // k) % 2 == 0 else 0
print(int(np.max(np.sum(check, axis=0))))