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)

import numpy as np

def judge(k,x,y):
    return (x//k + y//k)%2

n,k = map(int,input().split())
x = []
y = []
c = []
for i in range(n):
    s = input().split()
    x.append(int(s[0]))
    y.append(int(s[1]))
    if s[2] == "W":
        c.append(0)
    else:
        c.append(1)

ans = 0
for i in range(k):
    x_tmp = np.array(x) + i
    for j in range(k):
        y_tmp = np.array(y) + j
        for l in range(n):
            if judge(k,x_tmp[l],y_tmp[l]) == c[l]:
                count += 1
        tmp = max(count,n-count)
        ans = max(ans,tmp)
        count = 0
print(ans)