#include <stdio.h>
#include <stdlib.h>
int map[11][11];
int f[20][11][11];
#define max(a, b) ((a)>(b)?(a):(b))
 
int main(int argc, char **argv)
{
	freopen("fgqs.in","r",stdin);
	freopen("fgqs.out","w",stdout); 
    int i, j, k;
    int n;
    int a, b, c;
    scanf("%d", &n);
    while(scanf("%d%d%d", &a, &b, &c)){
        if(a == 0 && b == 0 && c == 0){
            break;
        }
        map[a][b] = c;
    }
    for(i = 1; i <= 2 * n - 1; i++){
        for(j = 1; j <= i; j++){
            for(k = 1; k <= i; k++){
                if(j == k){
                    c = map[j][i - j + 1];
                }else{
                    c = map[j][i - j + 1] + map[k][i - k + 1];
                }
                f[i][j][k] = max(f[i][j][k], f[i - 1][j - 1][k - 1] + c);
                f[i][j][k] = max(f[i][j][k], f[i - 1][j - 1][k] + c);
                f[i][j][k] = max(f[i][j][k], f[i - 1][j][k - 1] + c);
                f[i][j][k] = max(f[i][j][k], f[i - 1][j][k] + c);
            }
        }
    }
    printf("%d\n", f[2 * n - 1][n][n]);
    return 0;
}