学步园

#include<iostream>
#include<cstdio>
using namespace std;
inline int read(){
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
} 
int n,r,mx,my,ans,f[5005][5005];
int main(){
	n=read();r=read();
	for(int i=1;i<=n;i++){
		int x=read(),y=read(),v=read();
		f[x+1][y+1]=v;
		mx=max(x+1,mx);my=max(y+1,my);
	}
	mx=min(mx+r,5001);my=min(my+r,5001);
	for(int i=1;i<=mx;i++)
		for(int j=1;j<=my;j++){
			f[i][j]+=f[i-1][j]+f[i][j-1]-f[i-1][j-1];
			if(i>=r&&j>=r)ans=max(ans,f[i][j]-f[i-r][j]-f[i][j-r]+f[i-r][j-r]);
		}
	printf("%d",ans);
	return 0;
}