// https://judge.yosupo.jp/submission/198014

#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
istream &operator>>(istream &is, modint &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint &a) { return os << a.val(); }
istream &operator>>(istream &is, modint998244353 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint998244353 &a) { return os << a.val(); }
istream &operator>>(istream &is, modint1000000007 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint1000000007 &a) { return os << a.val(); } 

typedef long long ll;
typedef vector<vector<int>> Graph;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define FOR(i,l,r) for (int i = l;i < (int)(r); i++)
#define rep(i,n) for (int i = 0;i < (int)(n); i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define my_sort(x) sort(x.begin(), x.end())
#define my_max(x) *max_element(all(x))
#define my_min(x) *min_element(all(x))
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF = (1<<30) - 1;
const ll LINF = (1LL<<62) - 1;
const int MOD = 998244353;
const int MOD2 = 1e9+7;
const double PI = acos(-1);
vector<int> di = {1,0,-1,0};
vector<int> dj = {0,1,0,-1};

#ifdef LOCAL
#  include <debug_print.hpp>
#  define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define debug(...) (static_cast<void>(0))
#endif

using S = long long;
using F = long long;

S op(S a, S b){ return std::max(a, b); }
S e(){ return -LINF; }
S mapping(F f, S x){ return f+x; }
F composition(F f, F g){ return f+g; }
F id(){ return 0; }


int main(){
    cin.tie(0);
    ios_base::sync_with_stdio(false);

    ll N, A; 
    cin >> N >> A;
    A *= 2LL;
    vector<ll> X(N), Y(N), V(N);
    vector<ll> xs(4 * N), ys(4 * N);
    rep(i, N) {
        cin >> X[i] >> Y[i] >> V[i];
        X[i] *= 2LL;
        Y[i] *= 2LL;

        xs[4 * i + 0] = X[i] - A;
        xs[4 * i + 1] = X[i] - A + 1;
        xs[4 * i + 2] = X[i];
        xs[4 * i + 3] = X[i] + 1;

        ys[4 * i + 0] = Y[i] - A;
        ys[4 * i + 1] = Y[i] - A + 1;
        ys[4 * i + 2] = Y[i];
        ys[4 * i + 3] = Y[i] + 1;
    }
    sort(all(xs));
    xs.erase(unique(all(xs)), xs.end());
    int W = xs.size();

    sort(all(ys));
    ys.erase(unique(all(ys)), ys.end());
    int H = ys.size();

    vector<vector<array<ll, 3>>> query(H + 1);
    rep(i, N) {
        int l = distance(xs.begin(), lower_bound(all(xs), X[i] - A));
        int r = distance(xs.begin(), upper_bound(all(xs), X[i]));
        query[distance(ys.begin(), lower_bound(all(ys), Y[i] - A))].push_back({l, r, V[i]});
        query[distance(ys.begin(), upper_bound(all(ys), Y[i]))].push_back({l, r, -V[i]});
    }

    lazy_segtree<S, op, e, F, mapping, composition, id> seg(vector<S>(W + 1));

    ll ans = -LINF;
    rep(h, H + 1) {
        for(auto [l, r, w] : query[h]) seg.apply(l, r, w);
        chmax(ans, seg.all_prod());
    }

    cout << ans << endl;
}