代码：

#include <bits/stdc++.h>

#define ONLINE_JUDGE
#define ll long long

int n, m;
int x, y, v[5005][5005] = {0}, a[5005][5005] = {0}, maxx = 0, maxy = 0;

int read() {
	int x = 0, sign = 1;
	char ch = getchar_unlocked();
	for (; !isdigit(ch); ch = getchar_unlocked()) if (ch == '-') sign = -1;
	for (; isdigit(ch); ch = getchar_unlocked()) x = x * 10 + ch - '0';
	return x * sign;
}

int main() {
	#ifndef ONLINE_JUDGE
	freopen("input.in", "r", stdin);
	freopen("output.out", "w", stdout);
	#endif

	n = read();
	m = read();
	for (int i = 1; i <= n; i++) {
		x = read() + 1;
		y = read() + 1;
		a[x][y] += read();
		v[x][y] = v[x - 1][y] + v[x][y - 1] - v[x - 1][y - 1] + a[x][y];
		maxx = std::max(maxx, x);
		maxy = std::max(maxy, y);
	}

	if (m > maxx) maxx = m;
	if (m > maxy) maxy = m;

	int ans = 0;
	for (int i = m; i <= maxx + 1 - m; i++) {
		for (int j = m; j <= maxy + 1 - m; j++) {
			int cur = v[i][j] - v[i - m][j] - v[i][j - m] + v[i - m][j - m];
			ans = std::max(ans, cur);
		}
	}

	printf("%d", ans);
	return 0;
}