program nume;
var f,g:TEXT;
    n,m,max,x,y,s:longint;
    a:array[-10..100,-10..100] of integer;
begin
assign(f,'flip.test');
assign(g,'flipout.test');
reset(f);
rewrite(g);
read(f,n);
read(F,m);
max:=0;
for x:=1 to n do for y:=1 to m do read(f,a[x,y]);
for x:=1 to n do for y:=1 to m do begin
                                  max:=max+a[x,y];
                                  s:=s+a[x,y];
                                  end;
for x:=1 to n do for y:=1 to m do begin
                                  if(s+(a[x,y]*(-1))-a[x,y]>max) then begin
                                                                        s:=s+(a[x,y]*(-1))-a[x,y];
                                                                        max:=s+(a[x,y]*(-1))-a[x,y];
                                                                        end;
                                  end;
write(g,max);
close(f);
close(g);
end.