var f,g:text;
i,j,n,m,sp,sn,s:longint;
a:array[1..16,1..16] of longint;
vl,vc:array[1..16] of integer;
begin
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 begin
sp:=0;
sn:=0;
for j:=1 to m do
if a[i,j]<0 then sn:=sn+a[i,j]
            else sp:=sp+a[i,j];
vl[i]:=sp+sn;
end;
for j:=1 to m do begin
sp:=0;
sn:=0;
for i:=1 to n do
if a[i,j]<0 then sn:=sn+a[i,j]
            else sp:=sp+a[i,j];
vc[j]:=sp+sn;
end;
for i:=1 to n do
if vl[i]<0 then for j:=1 to m do a[i,j]:=-a[i,j];
for j:=1 to m do
if vc[j]<0 then for i:=1 to n do a[i,j]:=-a[i,j];
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);
end.