#include<bits/stdc++.h>
using namespace std;
const int i=10;
int s[i][i],f[i<<1][i][i],n;
int main() {
	scanf("%d",&n);
	memset(s,0,sizeof(a));
	while (1) {
		int x,y,z;
		scanf("%d %d %d",&x,&y,&z);
		if (x==0 && y==0 && z==0) break;
		s[x][y]=z;
	}
	f[0][1][1]=a[1][1];
	for (int i=1; i<=2*n-2; i++)
		for (int a=1; a<=n; a++)
			for (int x2=1; x2<=n; x2++) {
				int y1=i+2-x1,y2=i+2-x2;
				if (y1<1 || y2<1) continue;
				f[i][a][x2]=max(f[i-1][a][x2],max(f[i-1][a-1][x2],max(f[i-1][a][x2-1],f[i-1][a-1][x2-1])))+s[a][y1]+a[x2][y2];
				if (a==x2 && y1==y2) f[i][x1][x2]-=s[a][y1];
			}
	printf("%d",f[n*2-2][n][n]);
	return 0;
}