//这里填你的代码^^
#include<stdio.h>
#include<iostream>
using namespace std;
const int N = 15;
int w[N][N];
int f[N + N][N][N];
int main() {
    int n;//边长
    cin >> 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 = 1; i1 <= n; i1++)
            for (int i2 = 1; i2 <= n; i2++)
            {
                int j1 = k - i1;
                int j2 = k - i2;//求出纵坐标
                if (j1 >= 1 && j1 <= n && j2 >= 1 && j2 <= n) {
                    int t = w[i1][j1];
                    if (i1 != i2) t += w[i2][j2];
                    int& x = f[k][i1][i2];
                    x = max(x, f[k - 1][i1 - 1][i2 - 1]+t);//下下
                    x = max(x, f[k - 1][i1][i2 - 1]+t);//右下
                    x = max(x, f[k - 1][i1 - 1][i2]+t);//下右
                    x = max(x, f[k - 1][i1][i2]+t);//右右
                }
            }
    cout << f[2 * n][n][n];
    return 0;
}
//注意代码要放在两组三个点之间，才可以正确显示代码高亮哦~