program flip;
var f,g:text;
    i,j,m,n:byte;
    s:integer;
    a:array[1..16,1..16] of longint;
begin
assign(f,'flip.in');reset(f);
assign(g,'flip.out');rewrite(g);
read(f,n);
readln(f,m);
for i:=1 to n do
   for j:=1 to m do
       read(f,a[i,j]);
if n>m then begin
   for i:=1 to m do begin
       s:=0;
       for j:=1 to n do
           s:=s+a[j,i];
       if s<0 then
          for j:=1 to n do
              a[j,i]:=a[j,i]*(-1);end;
   for i:=1 to n do begin
       s:=0;
       for j:=1 to m do
           s:=s+a[i,j];
       if s<0 then
          for j:=1 to m do
              a[i,j]:=a[i,j]*(-1);end;end
else begin
for i:=1 to n do begin
       s:=0;
       for j:=1 to m do
           s:=s+a[i,j];
       if s<0 then
          for j:=1 to m do
              a[i,j]:=a[i,j]*-1;end;
   for i:=1 to m do begin
       s:=0;
       for j:=1 to n do
           s:=s+a[j,i];
       if s<0 then
          for j:=1 to n do
              a[j,i]:=a[j,i]*-1;end;end;
s:=0;
for i:=1 to n do
   for j:=1 to n do
       s:=s+a[i,j];
write(g,s);
close(f);
close(g);
end.