C++ :

#include<iostream>
#define N 51
using namespace std;
int max(int a,int b){return a>b?a:b;}
int sum[N][N][N][N]={0};
int c[N][N]={0};
int main()
{
    int n,m,i,j,h,k,a,b;
    cin>>m>>n;
    for(i=1;i<=m;i++)
      for(j=1;j<=n;j++)
        cin>>c[i][j];
    for(i=1;i<=m;i++)
      for(j=1;j<=n;j++)
        for(h=1;h<=m;h++)
          for(k=1;k<=n;k++)
          {
            a=max(sum[i-1][j][h-1][k],sum[i][j-1][h][k-1]);
            b=max(sum[i-1][j][h][k-1],sum[i][j-1][h-1][k]);
            sum[i][j][h][k]=max(a,b)+c[i][j];
            if(i!=h&&j!=k)sum[i][j][h][k]+=c[h][k];
          }
    cout<<sum[m][n][m][n];
    return 0;
}

Pascal :

var
  f:array[-50..101,-50..51,-50..51]of longint;
  a:array[-100..100,-100..100]of longint;
  n,i,j,k,m,maxn,s,minn,xxx:longint;
function max(a,b:longint):longint;
 begin
if a>b then max:=a else max:=b
end;
begin
  //assign(input,'message.in');   reset(input);
  //assign9output,'message.out'); rewrite(output);
  readln(n,m);
  for i:=1 to n do
   for j:=1 to m do read(a[i,j]);      fillchar(f,sizeof(f),0);
  xxx:=m+n-2;
  for k:=2 to xxx do
   begin

     for i:=1 to n do
      for j:=i+1 to n do
        begin
          if abs(j-i) > 1 then
           begin
              f[k,i,j]:=max(f[k-1,i,j],f[k-1,i,j-1]);
              f[k,i,j]:=max(f[k,i,j],f[k-1,i-1,j]);
              f[k,i,j]:=max(f[k,i,j],f[k-1,i-1,j-1]);
              inc(f[k,i,j],a[i,k+1-i]+a[j,k+1-j]);
           end else

           begin
             f[k,i,j]:=max(f[k-1,i,j],f[k-1,i-1,j-1]);
             f[k,i,j]:=max(f[k,i,j],f[k-1,i-1,j]);
              inc(f[k,i,j],a[i,k+1-i]+a[j,k+1-j]);
           end;

        end;
   end;
  writeln(f[xxx,n-1,n]);
//  close(input); rewrite(output);
end.