var a:array[1..200,1..200] of longint;
    n,m,j,i,s1,s2,s:longint;

procedure citire;
 begin
  assign(input,'flip.in');reset(input);
  assign(output,'flip.out');rewrite(output);
  read(n);
  readln(m);
   for i:=1 to n do
    for j:=1 to m do
     read(a[i,j]);
  close(input);
 end;

procedure prelucrare;
 begin

 end;

procedure inmultirecui;
 begin
  for j:=1 to m do
   a[j,i]:=a[j,i]*(-1);
 end;

procedure inmultirecuj;
 begin
  for i:=1 to n do
   a[i,j]:=a[i,j]*(-1);
 end;

procedure afisare;
 begin
  for i:=1 to n do
   begin
    for j:=1 to m do
     s1:=s1+a[i,j];
    if s1<0 then
     inmultirecui;
    s1:=0;
   end;
  for j:=1 to m do
   begin
    for i:=1 to n do
     s2:=s2+a[i,j];
    if s2<0 then
     inmultirecuj;
    s2:=0;
   end;
  for i:=1 to n do
   for j:=1 to m do
    s:=s+a[i,j];
  write(s);

 end;

begin
 citire;
 afisare;
 close(output);
end.