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