program unu;
var N,M,i,j,k,s:integer;
    a:array[1..16,1..16] of integer;
    s1,s2:array[1..16] of integer;
    f:text;
    ok1,ok2:boolean;
begin
assign(f,'flip.in');reset(f);
readln(f,N,M);
for i:=1 to N do begin
         for j:=1 to M do begin
                          read(f,a[i,j]);
                          s1[i]:=s1[i]+a[i,j];
                          end;
             readln(f);
             end;
close(f);
for j:=1 to M do
            for i:=1 to N do s2[j]:=s2[j]+a[i,j];
repeat
      ok1:=true;
      ok2:=true;
      for i:=1 to N do if s1[i]<0 then begin
                                       s1[i]:=-s1[i];
                                       for k:=1 to M do a[i,k]:=-a[i,k];
                                       ok1:=false;
                                       end;
      for i:=1 to M do if s2[i]<0 then begin
                                       s2[i]:=-s2[i];
                                       for k:=1 to N do a[k,i]:=-a[k,i];
                                       ok2:=false;
                                       end;
until ok1 and ok2;

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.