var a:array[1..50,1..50] of integer;

f:array[0..100,0..50,0..50] of int64;

i,j,k,n,m:longint;

function max(a,b,c,d:int64):int64;

begin

max:=a;

if b>max then max:=b;

if c>max then max:=c;

if d>max then max:=d;

end;

begin

readln(m,n);

for i:=1 to m do

for j:=1 to n do

read(a);

f[0,1,1]:=a[1,1];

f[1,1,2]:=a[2,1]+a[1,2]; f[1,2,1]:=a[1,2]+a[2,1];

for i:=2 to m+n-3 do

for j:=1 to n do

for k:=1 to n do

if ((jk) or ((j=n) and (k=n))) and (i+2>j) and (i+2>k) then

f:=max(f,f,f,f)+a[j,i+2-j]+a[k,i+2-k];

writeln(f[m+n-3,n,n-1]);

end.