#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<climits>
#include<cstdlib>
#include<ctime>
#include<cctype>
#include<algorithm>
#include<set>
#include<map>
#include<vector>
#include<stack>
#include<queue>
#include<deque>
#include<string>
#include<sstream>
#include<iomanip>
using namespace std;
//=====================struct declaration======================

//=====================var declarartion========================
const int maxn=10+10;
int a[maxn][maxn],f[maxn][maxn][maxn][maxn];

int n,r,s,t,x,y,z;
//=====================function declaration====================

//=====================main code===============================
int main()
{
	freopen("fgqs.in","r",stdin);
	freopen("fgqs.out","w",stdout);
	
	scanf("%d",&n);
	while(1)
	{
		scanf("%d%d%d",&r,&s,&t); if(r==0) break;
		a[r][s]=t;
	}
	
	for(int i=1; i<=n; i++)
	for(int j=1; j<=n; j++)
	for(int i2=1; i2<=n; i2++)
	for(int j2=1; j2<=n; j2++)
	{
		x=max(f[i-1][j][i2-1][j2],f[i-1][j][i2][j2-1]);
		y=max(x,f[i][j-1][i2-1][j2]);
		z=max(y,f[i][j-1][i2][j2-1]);
		if(i==i2 && j==j2)
			f[i][j][i2][j2]=z+a[i][j];
		else
			f[i][j][i2][j2]=z+a[i][j]+a[i2][j2];
	}
	
	cout<<f[n][n][n][n]<<endl;
	
	return 0;
}