var f:text;
    n,m,s,i,j,s1,s2:longint;
    a:array[1..16,1..16]of longint;
    ok:boolean;
begin
     assign(f,'flip.in');
     reset(f);
              read(f,n,m);
              for i:=1 to n do
              for j:=1 to m do
                  read(f,a[i,j]);
     close(f);
     ok:=true;
     while ok do
     begin
          ok:=false;
     for i:=1 to n do
     begin
          s1:=0;
          for j:=1 to m do
          begin
              s1:=s1+a[i,j];
          end;
          if s1<0 then
          begin
               for j:=1 to m do
                   a[i,j]:=-a[i,j];
               ok:=true;
          end;
     end;

     for i:=1 to m do
     begin
          s1:=0;
          for j:=1 to n do
          begin
              s1:=s1+a[j,i];
          end;
          if s1<0 then
          begin
               for j:=1 to n do
                   a[j,i]:=-a[j,i];
               ok:=true;
          end;
     end;

     end;
     for i:=1 to n do
     for j:=1 to m do
     s:=s+a[i,j];
     assign(f,'flip.out');
     rewrite(f);
                write(f,s);
     close(f);
end.