#include<bits/stdc++.h>
using namespace std;
const int M=5005; 
int n, r, ans;
int sum[M][M];
int main()
{
   cin >> n >> r;
   for(int i = 1; i <= n; i++)
   {
       int x, y, z;
       cin>>x>>y>>z;
       sum[x + 1][y + 1] = z;
   }
   for(int i = 1; i <= 5000; i++)
       for(int j = 1; j <= 5000; j++)
           sum[i][j] += (sum[i - 1][j] + sum[i][j - 1] - sum[i - 1][j - 1]); 
   for(int i = r; i <= 5000; i++)
       for(int j = r; j <= 5000; j++)
           ans = max(ans, sum[i][j] - sum[i - r][j] - sum[i][j - r] + sum[i - r][j - r]);
   cout << ans;
   return 0;   

}