#include<cstdio>
#include<algorithm>
using namespace std;
int a[51][51];
int sum[51][51][51][51];
int n,i,j,h,k,x,y,z;
int hh()
{
	scanf("%d%d%d%d",&n,&x,&y,&z);
	while(x&&y&&z)
	{
		a[x][y]=z;
		scanf("%d%d%d",&x,&y,&z);
	}
	for(i=1;i<=n;i++)
	   for(j=1;j<=n;j++)
	      for(h=1;h<=n;h++)
	         for(k=1;k<=n;k++)
	         {
	         	int temp1=max(sum[i-1][j][h-1][k],sum[i][j-1][h][k-1]);
	         	int temp2=max(sum[i-1][j][h][k-1],sum[i][j-1][h-1][k]);
	         	sum[i][j][h][k]=max(temp1,temp2)+a[i][j];
	         	if(i!=h&&j!=k) sum[i][j][h][k]+=a[h][k];
			 }
			 printf("%d\n",sum[n][n][n][n]);
			 return 0;
 } 
int Main()
{
	freopen("fgqs.in","r",stdin);
    freopen("fgqs.out","w",stdout);
	hh();
 } 
 int work=Main();
 int main(){;
 }