var f,g:text;i,n,m,j:integer;a:array[1..16,1..16]of longint;s:longint;
v,u:array[1..16]of longint;
begin
assign(f,'flip.in');reset(f);
assign(g,'flip.out');rewrite(g);
readln(f,m,n);
for i:=1 to m do
for j:=1 to n do
begin
read(f,a[i,j]);
v[i]:=v[i]+a[i,j];
u[j]:=u[j]+a[i,j];
end;
for i:=1 to m do
for j:=1 to n do
begin
if(v[i]<0)or(u[j]<0)then a[i,j]:=a[i,j]*(-1);
s:=s+a[i,j];
end;
write(g,s);
close(f);close(g);
end.