program Val24;
var a:array[1..16,1..16] of longint;
    s,i,j:longint;
    n,m:byte;
    ok:boolean;
    f,g:text;
begin
assign(f,'flip.in');
reset(f);
assign(g,'flip.out');
rewrite(g);
read (f,n,m);
for i:=1 to n do
    begin
         for j:=1 to m do
             begin
                  read(f,a[i,j]);
             end;
    end;
repeat
ok:=true;
for i:=1 to n do
    begin
    s:=0;
         for j:=1 to m do
         begin
         s:=s+a[i,j];
         end;
          if s<0 then
            for j:=1 to m do
                begin
                a[i,j]:=-a[i,j];
                ok:=false;
                end;
    end;
for J:=1 to m do
    begin
    s:=0;
    for i:=1 to n do
        begin
        s:=s+a[i,j];
    end;
     if s<0 then
      for i:=1 to n do
          begin
          ok:=false;
          a[i,j]:=-a[i,j];
         end;
    end;

until ok=true;
   s:=0;
for i:=1 to n do
    for j:=1 to m do
        s:=s+a[i,j];
write(g,s);
close(g);
close(f);
end.