var n,m,i,j:byte;
    s:longint;
    a:array[1..16,1..16]of longint;
    f,g:text;
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
for j:=1 to m do
begin
if a[i,j]<0 then a[i,j]:=a[i,j]*-1;
s:=s+a[i,j];
end;
write(g,s);
close(f);
close(g)
end.