program asd;
var f,g:text;
    a:array[1..100,1..100]of integer;
    i,j,n,m,sum:integer;
begin
assign(f,'flip.in'); reset(f);
assign(g,'flip.out'); rewrite(g);
readln(f,n,m);
for i:=1 to n do
begin
for j:=1 to m do
read(f,a[i,j]);
readln(f);
end;
for j:=1 to m do
begin
sum:=0;
for i:=1 to n do
sum:=sum+a[i,j];
if sum<=0 then begin
   for i:=1 to n do
   a[i,j]:=a[i,j]*-1;
               end;
end;
for i:=1 to n do
begin
sum:=0;
for j:=1 to m do
sum:=sum+a[i,j];
if sum<=0 then begin
   for j:=1 to m do
   a[i,j]:=a[i,j]*-1;
               end;
end;
sum:=0;
for i:=1 to n do
for j:=1 to m do
sum:=sum+a[i,j];
writeln(g,sum);
close(f);
close(g);
end.