var     m,n,i,j,s,a,b:longint;
        v:array[0..20,0..20]of longint;
        gata:boolean;
begin

assign(input,'flip.in');
assign(output,'flip.out');

reset(input);
read(m,n);

for i:=1 to m do
for j:=1 to n do
begin
        read(v[i,j]);
end;

repeat
gata:=true;
for j:=1 to n do
begin
a:=0;
b:=0;
for i:=1 to m do
begin

        a:=a+v[i,j];
        b:=b-v[i,j];

end;
if b>a then
begin
for i:=1 to m do
v[i,j]:=-v[i,j];
gata:=false;
end;
end;

for i:=1 to m do
begin
a:=0;
b:=0;
for j:=1 to n do
begin

        a:=a+v[i,j];
        b:=b-v[i,j];

end;
if b>a then
begin
for j:=1 to n do
v[i,j]:=-v[i,j];
gata:=false;
end;

end;

until gata;

s:=0;
for i:=1 to m do
for j:=1 to n do
begin
        s:=s+v[i,j];
end;

rewrite(output);
write(s);
close(output);

end.