record->here

代码：

#include<bits/stdc++.h>
using namespace std;
const int N=5e3+5;
int s[N][N];
int x,y,v,n,m;
signed main(){
//   freopen("123.in","r",stdin);
//   freopen("123.out","w",stdout);
    cin>>n>>m;
    for(int i=1;i<=n;i++){
        cin>>x>>y>>v;
        s[x][y]+=v;
    }
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            s[i][j]+=s[i-1][j]+s[i][j-1]-s[i-1][j-1];
        }
    }
    int ans=0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            if(i-m>=0&&j-m>=0) ans=max(s[i][j]-s[i-m][j]-s[i][j-m]+s[i-m][j-m],ans);
        }
    }
    cout<<ans;
    return 0;
}