var a:array[1..16,1..16] of longint;
    i,j,n,m:integer;
    s:longint;
function suml(k:integer):longint;
var p:integer;
    s1:longint;
begin
s1:=0;
for p:=1 to m do
    s1:=s1+a[k,p];
suml:=s1;
end;

function sumc(K:integer):longint;
var p:integer;
    s1:longint;
begin
s1:=0;
for p:=1 to n do
    s1:=s1+a[p,k];
sumc:=s1;
end;

procedure flipl(K:integer);
var P:integer;
begin
for p:=1 to m do
    a[k,p]:=a[k,p]*(-1);
end;

procedure flipc(k:integer);
var p:integer;
begin
for p:=1 to n do
    a[p,k]:=a[p,k]*(-1);
end;

begin
assign(input,'flip.in');
assign(output,'flip.out');
reset(input);
rewrite(output);
readln(n,m);
for i:=1 to n do
    begin
    for j:=1 to m do
        read(a[i,j]);
    readln;
    end;
for i:=1 to n do
    if suml(i)<0 then
       flipl(i);



for j:=1 to m do
    if sumc(j)<0 then
       flipc(j);
s:=0;
for i:=1 to n do
    for j:=1 to m do
        s:=s+a[i,j];
writeln(s);
close(input);
close(output);
end.