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