#include <bits/stdc++.h>
#define INT long long int
using namespace std;
INT a[40][40][40], b[40][40][40], n;
INT f(int x, int y, int z, int k)
{
    if( x == n or y == n or z == n or x == -1 or y == -1 or z == -1 )
        return -98765432111111;
    if( k == 0 )
    {
        if( x == n-1 and y == n-1 and z == n-1 ) return f(n-1, n-1, n-1, 1);
        INT ret = 0;
        b[x][y][z] = 1;
        ret = max( ret, f(x+1, y, z, k) + a[x+1][y][z] );
        ret = max( ret, f(x, y+1, z, k) + a[x][y+1][z] );
        ret = max( ret, f(x, y, z+1, k) + a[x][y][z+1] );
        b[x][y][z] = 0;
        return ret;
    }
    else
    {
        if( x == 0 and y == 0 and z == 0 ) return 0;
        INT ret = 0;
        ret = max( ret, f(x-1, y, z, k) + (b[x-1][y][z]?0:a[x-1][y][z]) );
        ret = max( ret, f(x, y-1, z, k) + (b[x][y-1][z]?0:a[x][y-1][z]) );
        ret = max( ret, f(x, y, z-1, k) + (b[x][y][z-1]?0:a[x][y][z-1]) );
        return ret;
    }
}
int main()
{
    cin>>n;
    for(int i = 0 ; i < n ; i++ )
        for(int j = 0 ; j < n ; j++ )
            for(int k = 0 ; k < n ; k++ )
                cin>>a[i][j][k];
    cout<<f(0, 0, 0, 0) + a[0][0][0]<<endl;
}