#include <iostream>
#include <algorithm>

using namespace std;

const int N = 15;

int n;
int w[N][N];
int f[N * 2][N][N];

int main()
{
    scanf("%d", &n);

    int a, b, c;
    while (cin >> a >> b >> c, a || b || c) w[a][b] = c;

    for (int k = 2; k <= n + n; k ++ )
        for (int i1 = max(1, i1 - n); i1 <= n && i1 < k; i1 ++ )
            for (int i2 = max(1, i1 - n); i2 <= n && i2 < k; i2 ++ )
            {
                int j1 = k - i1, j2 = k - i2;
                int &x = f[k][i1][i2];
                if(i1 != i2 || k == 2  || k == n + n){
                    int t = w[i1][j1];
                    if(i1 != i2)
                       t += w[i2][j2];
                    for(int g = 0; g <= 1; g ++ ){
                        for(int h = 0; h <= 1; h ++ ){
                            x = max(x, f[k - 1][i1 - g][i2 - h] + t);
                        }
                    }   
                }    
            }

    printf("%d\n", f[n + n][n][n]);
    return 0;
}