#include<bits/stdc++.h>

using namespace std;

int n,g[][];

int f[][][][];

inline int max(int x,int y)

{

    return x>y?x:y;

}

int main()

{

    int i,j,k,l;

    scanf("%d",&n);

    while(true)

    {

        int x,y,v;

        scanf("%d%d%d",&x,&y,&v);

        g[x][y]=v;

        if(x==&&y==&&v==) break;

    }

    for(i=;i<=n;i++)

     for(j=;j<=n;j++)

      for(k=;k<=n;k++)

       for(l=;l<=n;l++)

       {

           f[i][j][k][l]=max(max(f[i-][j][k-][l],f[i-][j][k][l-]),max(f[i][j-][k][l-],f[i][j-][k-][l]))

           +g[i][j]+g[k][l];

         if(i==k&&j==l) f[i][j][k][l]-=g[i][j];

       }

    printf("%d",f[n][n][n][n]);

    return ;

}