#include<bits/stdc++.h>
using namespace std;
const int N=12;
int f[N*2][N][N];
int w[N][N];
int n;
int main()
{
    cin>>n;
    int a,b,c;
    while(cin>>a>>b>>c,a||b||c)w[a][b]=c;
    for(int k=2;k<=2*n;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 t=w[i1][j1];
                    if(i1!=i2)t+=w[i2][j2];
                    int a=f[k-1][i1-1][i2-1],b=f[k-1][i1-1][i2],c=f[k-1][i1][i2-1],d=f[k-1][i1][i2];
                    f[k][i1][i2]=max(max(a,b),max(c,d))+t;
                }
            }
        }
    }
    cout<<f[n*2][n][n];
    return 0;
}