var f,g:text;
 a:array[1..20,1..20]of integer;i,j,m,n,i1,s:integer;v,b:array[1..20]of integer;
begin
assign(f,'flip.in');reset(f);
assign(g,'flip.out');rewrite(g);s:=0;
readln(f,n,m);
for i:=1 to n do
begin
for j:=1 to m do
read(f,a[i,j]);
end;
for i:=1 to n do
begin
v[i]:=0;
for j:=1 to m do
v[i]:=v[i]+a[i,j];
end;
for i1:=1 to m do
begin
b[i1]:=0;
for i:=1 to n do
for j:=1 to m do
if j=i1 then b[i1]:=b[i1]+a[i,j];end;
for i:=1 to n do
for j:=1 to m do
if (v[i]>0)then a[i,j]:=a[i,j]*(-1);
for i1:=1 to m do
for i:=1 to n do
for j:=1 to m do
if (i1=j)and(b[i1]>0)then a[i,j]:=a[i,j]*(-1);
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.