C :

#include<stdio.h>
int m,n,a[11][11];
int x,y,z;
int f[11][11][11][11];
int my_max(int,int,int,int);
int main()
{
//	freopen("fgqs.in","r",stdin);
//	freopen("fgqs.out","w",stdout);
	scanf("%d",&n);
	    while(1)
		{
			scanf("%d%d%d",&x,&y,&z);
			if(x==0&&y==0&&z==0) break;
			a[x][y]=z;
		}
		for(int i1=1;i1<=n;i1++)
			for(int j1=1;j1<=n;j1++)
				for(int i2=1;i2<=n;i2++)
					for(int j2=1;j2<=n;j2++)
					{
						f[i1][j1][i2][j2]=my_max(f[i1-1][j1][i2][j2-1],
											  f[i1-1][j1][i2-1][j2],
											  f[i1][j1-1][i2-1][j2],
											  f[i1][j1-1][i2][j2-1]);
						f[i1][j1][i2][j2]+=a[i1][j1];
						if(i1!=i2||j1!=j2)  f[i1][j1][i2][j2]+=a[i2][j2];
					}
		printf("%d",f[n][n][n][n]);
}
int my_max(int a,int b,int c,int d)
{
	int tot=0;
	if(tot<a) tot=a;
	if(tot<b) tot=b;
	if(tot<c) tot=c;
	if(tot<d) tot=d;
	return tot;
}

C++ :

#include <cstdio>

using namespace std;
 
int f[11][11][11][11];
int c[11][11];
int n;
int main()
{
	int n ;
	scanf("%d",&n) ;
	int a , b , t ;
	for (int i = 1 ; true ; i ++ )
	{
		scanf("%d%d%d",&a,&b,&t);
		if (!a && !b && !t) break;
		else c[a][b]=t;
	}
	for (int i = 1 ; i <= n ; i ++ )
		for (int j = 1 ; j <= n ; j ++ )
			for (int k = 1 ; k <= n ; k ++ )
				for (int p = 1 ; p <= n ; p ++ )
				{
					f[i][j][k][p] = f[i-1][j][k-1][p];
					if (f[i-1][j][k][p-1] > f[i][j][k][p])f[i][j][k][p] = f[i-1][j][k][p-1];
					if (f[i][j-1][k-1][p] > f[i][j][k][p])f[i][j][k][p] = f[i][j-1][k-1][p];
					if (f[i][j-1][k][p-1] > f[i][j][k][p])f[i][j][k][p] = f[i][j-1][k][p-1];
					f[i][j][k][p] += c[i][j];
					if(i != k || j != p) f[i][j][k][p] += c[k][p];
				}
	printf("%d\n",f[n][n][n][n]);
	return 0;
}