program Flip;
label i_reluare;
label j_reluare;
var n,m:byte;i,j,max,li,l,tr,co,c,s,q,w:integer;t:text; a,b : array[1..100,1..100] of longint;;
begin
assign(t,'flip.in');
reset(t);
readln(t,n,m);
for i := 1 to n do
begin
for j := 1 to m do
begin
read(t,a[i,j]);
b[i,j] := a[i,j];
end;
readln(t);
end;
close(t);
max := 0;
li := 1;
i_reluare:
for i := 1 to n do
begin
for l := li to i do
for tr := 1 to m do
b[l,tr] := b[l,tr] * (-1);
co := 1;
j_reluare:
for j := 1 to m do
begin
for c := co to j do
for tr := 1 to n do
b[tr,c] := b[tr,c] * (-1);
s := 0;
for q := 1 to n do
for w := 1 to m do
s := s + b[q,w];
if s > max then max := s;
for q := 1 to n do
for w := 1 to m do
b[q,w] := a[q,w];
for l := li to i do
for tr := 1 to m do
b[l,tr] := b[l,tr] * (-1);
if j = m then
while co < m do
begin
co := co + 1;
GOTO j_reluare;
end;
end;
for q := 1 to n do
for w := 1 to m do
b[q,w] := a[q,w];
end;
if i = n then
while li < n do
begin
li := li + 1;
GOTO i_reluare;
end;
assign(t,'flip.out');
rewrite(t);
write(t,max);
close(t);
end.