import sys
import re

def read(raw):
    sbuffer = list()
    for s in raw:
        if re.match('\s', s) is None:
            sbuffer.append(s)
        elif len(sbuffer) > 0:
            yield ''.join(sbuffer)
            sbuffer = list()
    yield ''.join(sbuffer)


pin = read(sys.stdin.read())

n = int(pin.next())
r = int(pin.next())
col = r
row = r

graph = [[0]*5002 for _ in range(5002)]

for _ in range(n):
    x = int(pin.next()) + 1
    y = int(pin.next()) + 1
    w = int(pin.next())

    graph[x][y] += w
    col = max(col, y)
    row = max(row, x)


for i in range(1, row+1):
    for j in range(1, col+1):
        graph[i][j] += graph[i][j-1] + graph[i-1][j] - graph[i-1][j-1]

res = 0
for i in range(r, row+1):
    for j in range(r, col+1):
        ans = graph[i][j] - graph[i-r][j] - graph[i][j-r] + graph[i-r][j-r]
        res = max(ans, res)
print res