program flip;
type matr=array[1..16,1..16] of integer;
var a:matr;
v,h:array[1..16] of integer;
i,j,m,n,k,s:integer;
f,g:text;

begin
k:=-1;
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]);

for i:=1 to n do
v[i]:=0;
for i:=1 to n do
for j:=1 to m do
v[i]:=v[i]+a[i,j];

for j:=1 to m do
h[j]:=0;
for i:=1 to n do
for j:=1 to m do
h[j]:=h[j]+a[i,j];

for i:=1 to n do
if v[i]<0 then
for j:=1 to m do
a[i,j]:=a[i,j]*k;

for j:=1 to m do
if h[j]<0 then
for i:=1 to n do
a[i,j]:=a[i,j]*k;

s:=0;
for i:=1 to n do
for j:=1 to m do
s:=s+a[i,j];

write(g,s);
close(f);
close(g);

readln;
end.