#include<bits/stdc++.h>
#define inc(i,l,r) for(int i=l;i<=r;i++)
#define dec(i,l,r) for(int i=l;i>=r;i++)
#define link(x) for(edge*j=h[x];j;j=j->next)
#define mem(a) memset(a,0,sizeof(a))
#define ll long long
#define succ(x) (1<<(x))
#define sqr(x) ((x)*(x))
#define lowbit(x) (x&(-x))
#define eps 1e-8
#define pi 3.1415926
#define NM 15
#define nm 300005
using namespace std;
ll read(){
ll x=0,f=1;char ch=getchar();
while(!isdigit(ch)){if(ch=='-')f=-1;ch=getchar();}
while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
return x*f;
}
int n,m,d[NM][NM][NM][NM],a[NM][NM],_x,_y,_t;
int main(){
n=read();
while(~scanf("%d%d%d",&_x,&_y,&_t)&&_x)a[_x][_y]=_t;
d[1][1][1][1]=a[1][1];
inc(i,1,n)inc(j,1,n)inc(k,1,n)inc(v,1,n){
d[i][j][k][v]=max(max(d[i-1][j][k-1][v],d[i-1][j][k][v-1]),max(d[i][j-1][k-1][v],d[i][j-1][k][v-1]));
d[i][j][k][v]+=a[i][j]+a[k][v];
if(i==k&&j==v)d[i][j][k][v]-=a[i][j];
}
printf("%d\n",d[n][n][n][n]);
return 0;
}
