Program p1;
var a:array[1..16,1..16] of integer;
i,j,n,m,y,x,s,s1: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   begin
for j:=1 to m do
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 begin
If s<0 then
a[i,x]:=-1*a[i,x];
end;
until(x=m);
y:=0;
repeat
y:=y+1;
s:=0;
for j:=1 to m do begin
s:=s+a[y,j];
end;
for j:=1 to m do begin
If s<0 then
a[y,j]:=-1*a[y,j];
end;
until(y=n);
s1:=0;
for i:=1 to n do
for j:=1 to m do
s1:=s1+a[i,j];
writeln(g,s1);
close(f);close(g);
end.