二位前缀

#include<iostream>
#include<algorithm>
using namespace std;
const int N=1e5+5,INF=0x3f3f3f3f;
typedef long long LL;
int n,x,y,v,r,ans=0;
int f[9241][5780];
int main()
{
	cin>>n>>r;
	int a=r,b=r;
	for(int i=1;i<=n;i++)
	{
		cin>>x>>y>>v;
		x++,y++;
		f[x][y]+=v;
		a=max(a,x);b=max(b,y);
	}
	for(int i=1;i<=a;i++)for(int j=1;j<=b;j++)f[i][j]+=f[i-1][j]+f[i][j-1]-f[i-1][j-1];
	for(int i=r;i<=a;i++)for(int j=r;j<=b;j++)ans=max(ans,f[i][j]-f[i-r][j]-f[i][j-r]+f[i-r][j-r]);
	cout<<ans;
	return 0;
}