type tablou=array [0..17]of byte;
     matrice=array [1..16,1..16]of longint;
var a:matrice;
    t1,t2:tablou;
    i,j,k,m,n,max,p,q,s,x,y:longint;
    f,g:text;
begin
assign(f,'flip.in');
assign(g,'flip.out');
reset(f);
rewrite(g);
read(f,n,m);
for i:=1 to n do
 for j:=1 to m do
  read(f,a[i,j]);
p:=1;
q:=1;
for i:=1 to n do
 p:=p*2;
for j:=1 to m do
 q:=q*2;
i:=1;
max:=-maxint;
while i<=p do
 begin
  j:=1;
  while j<=q do
   begin
    s:=0;
    for x:=1 to n do
      for y:=1 to m do
      if ((t1[x]=0)or(t2[y]=0))and((t1[x]=1)or(t2[y]=1)) then s:=s-a[x,y]
       else  s:=s+a[x,y];
     if s>max then max:=s;
     t2[m]:=t2[m]+1;
     y:=m;
     repeat
      if t2[y]=2 then begin
                       t2[y]:=0;
                       t2[y-1]:=t2[y-1]+1;
                       end;
      y:=y-1;
     until t2[y]<2;
     j:=j+1;
   end;
     t1[n]:=t1[n]+1;
     y:=n;
     repeat
      if t1[y]=2 then begin
                       t1[y]:=0;
                       t1[y-1]:=t1[y-1]+1;
                       end;
      y:=y-1;
     until t1[y]<2;
     i:=i+1;
     for x:=0 to m do
     t2[x]:=0;
  end;
write(g,max);
close(f);
close(g);
end.