Program p1;
var a:array[-10000..10000,-10000..10000] of integer;
var i,j,n,x,m,y:integer;
s:integer;
f,g:text;
begin
assign(f,'flip.in');reset(f);
assign(g,'flip.out');rewrite(g);
read(f,n);
read(f,m);

For i:=1 to n do
For j:=1 to m do
begin
read(f,a[i,j]);
read(f);
end;
x:=0;
repeat
x:=x+1;
s:=0;
For i:=1 to n do  begin
s:=s+a[i,x];
end;
For i:=1 to n do
If s<0 then
begin
a[i,x]:=-1*a[i,x]
end;
until(x=m);
y:=0;
repeat
s:=0;
y:=y+1;
For j:=1 to n do   begin
s:=s+a[y,j]
end;
For j:=1 to n do
If s<0 then
a[y,j]:=-1*a[y,j];
until(y=n);
s:=0;
For i:=1 to n do
for j:=1 to n do
s:=s+a[i,j];
writeln(g,s);
close(f);close(g);
end.