#include <algorithm>

 #include <cstdio>

 #include <cstring>

 #include <cmath>

 #include <iostream>

 #include <map>

 #include <queue>

 #include <set>

 #include <vector>

 using namespace std;

 #define max3(x, y, z) max(max((x), (y)), (z))

 #define min3(x, y, z) min(mix((x), (y)), (z))

 #define pb push_back

 #define ppb pop_back

 #define mk make_pair

 #define debug_l(a) cout << #a << " " << (a) << endl

 #define debug_b(a) cout << #a << " " << (a) << " "

 #define testin(filename) freopen((filename) ,"r",stdin)

 #define testout(filename) freopen((filename) ,"w",stdout)

 typedef long long ll;

 typedef unsigned long long ull;

 const double PI  = 3.14159265358979323846264338327;

 const double E   = exp();

 const double eps = 1e-;

 const int INF    = 0x3f3f3f3f;

 const int NINF   = 0xc0c0c0c0;

 const int maxn   = 3e3 + ;

 const int MOD    = 1e9 + ;

 int Map[maxn][maxn], Cur[maxn], dp[maxn][maxn];

 int main()

 {

     //testin("data1.in");

     int n;

     scanf("%d", &n);

     memset(Map, NINF, sizeof(Map));

     memset(Cur, , sizeof(Cur));

     memset(dp, , sizeof(dp));

     int vis =  + ( * (n - ));

     int cur =  * n - ;

     int i, j;

     for (int i = ; i < vis - n; i++) {

         if (i <= i % n)

             Cur[i] = i % n + ;

         else {

             if (n & )

                 Cur[i] = (i & ) ? n -  : n;

             else

                 Cur[i] = (i & ) ? n : n - ;

         }

     }

     for (int i = vis - ; i >= vis - n; i--)

         Cur[i] = vis - i;

     vector <int> v[vis];

     int temp;

     for (i = ; i < vis; i++)

     {

         for (j = ; j < Cur[i]; j++)

         {

             scanf("%d", &temp);

             v[i].push_back(temp);

         }

     }

     int len = cur /  + ;

     int flag = ;

     for (i = , j = n; i < len; i++, j++)

     {

         for (int l = , k = flag; l < j; l++, k++)

         {

             Map[i][l] = v[k][v[k].size() - ];

             v[k].pop_back();

             if (v[k].size() == )

                 flag++;

         }

     }

     for (j -= ; i < cur; i++, j--)

     {

         for (int l = (cur - j), k = flag; l < cur; l++, k++)

         {

             Map[i][l] = v[k][v[k].size() - ];

             v[k].pop_back();

             if (v[k].size() == )

                 flag++;

         }

     }

     dp[][] = Map[][];

     for (int i = ; i < cur; i++) {

         dp[][i] = Map[][i] + dp[][i - ];

         dp[i][] = Map[i][] + dp[i - ][];

     }

     for (int i = ; i < cur; i++)

         for (int j = ; j < cur; j++)

             dp[i][j] = Map[i][j] + max3(dp[i - ][j - ], dp[i - ][j], dp[i][j - ]);

     cout << dp[cur - ][cur - ] << endl;

     return ;

 }