{uses crt;}
var f,g:text;n,m:integer;s,i,j,ss:longint;a:array[1..20,1..20]of longint;
begin
assign(f,'flip.in');reset(f);
assign(g,'flip.out');rewrite(g);
readln(f,n,m);
{clrscr;}
for i:=1 to n do begin
s:=0;
for j:=1 to m do begin
read(f,a[i,j]);
s:=s+a[i,j];end;
if s<0 then
for j:=1 to m do
a[i,j]:=a[i,j]*-1;end;

{for i:=1 to n do begin
for j:=1 to m do
write(a[i,j],' '); writeln;end; writeln;}

ss:=0;
for i:=1 to m do begin
s:=0;
for j:=1 to n do
s:=s+a[j,i];
if s<0 then begin
for j:=1 to n do
a[j,i]:=a[j,i]*-1;
ss:=ss+(s*-1);end
else ss:=ss+s;end;
{for i:=1 to n do begin
for j:=1 to m do
write(a[i,j],' '); writeln;end;}
write(g,ss);
close(f);
close(g);
end.