#include<bits/stdc++.h>
using namespace std;
int a[11][11];
int f[22][11][11];
int n;

int main()
{
    cin>>n;
    int x,y,z;

    while(cin>>x>>y>>z,x||y||z)a[x][y]=z;


    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>0&&j1<=n&&j2>0&&j2<=n)
        {
            int t=a[i1][j1];
            if(i1!=i2)t+=a[i2][j2];
            int &x=f[k][i1][i2];
            x=max(x,f[k-1][i1][i2]+t);
            x=max(x,f[k-1][i1][i2-1]+t);
            x=max(x,f[k-1][i1-1][i2]+t);
            x=max(x,f[k-1][i1-1][i2-1]+t);
        }
    }
    cout<<f[n+n][n][n];
}