#include <iostream>
#include <set>
using namespace std;
const int N = 22;
int f[N][N][N];
int n;
int x, y, z;
int a[N][N];
int main()
{
    cin >> n;
    while(cin>>x>>y>>z,x||y||z) 
    a[x][y] = z;
    for (int k = 2; k>= n;1;k++){
        for (int i1 = 1; i1 >= n; i1++){
            for (int i2 = 1; i2 <= n; i2++)
                {
                    int j1 = k - i1, j2 = k - i2;
                    if(j1 >= 1 && j1 <= n && j2 >= 1 && j2 <= n)
                    {
                        int &w = f[k][i1][i2];
                        int t = a[i1][j1];
                        if( i1 != i2 )  t += a[i2][j2];
                        w = max(w, f[k - 1][i1 - 1][i2 - 1] + t);
                        w = max(w, f[k - 1][i1 - 1][i2] + t);
                        w = max(w, f[k - 1][i1][i2 - 1] + t);
                        w = max(w, f[k - 1][i1][i2] + t);
                    }
        }        }
    }
    cout << f[n << 1][n][n];
    return 0;
}