#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int f[20][20][20][20],q[20][20],n,w,y,z,ans;
int main()
{
	freopen("fgqs.in","r",stdin);
	freopen("fgqs.out","w",stdout);
	scanf("%d",&n);
	for(;;)
	{
	   scanf("%d%d%d",&w,&y,&z);
	   if(w==0&&y==0&&z==0)
	   {
	   	 break;
	   }
	   else q[w][y]=z;
	}
	for(int i=1;i<=n;i++)
	 for(int j=1;j<=n;j++)
      for(int k=1;k<=n;k++)
       for(int l=1;l<=n;l++)
       {
       	    f[i][j][k][l]=q[i][j]+q[k][l]+max(max(f[i-1][j][k-1][l],f[i][j-1][k-1][l]),max(f[i-1][j][k][l-1],f[i][j-1][k][l-1]));
	        if(i==k&&j==l) f[i][j][k][l]-=q[i][j];
	   }
	cout<<f[n][n][n][n];
	return 0;
}