var f1, f2:text;
a:array[1..100, 1..100] of integer;

 s,i,j,n,m:integer;

begin
assign(f1, 'flip.in');
reset(f1);
readln(f1, n,m);
writeln;
for i:=1 to n do
for j:=1 to m do 
read(f1, a[i,j]);
writeln;
for i:=1 to n do

for j:=1 to n do
 begin
if a[i,j]<0 then a[i,j]:=a[i,j]*(-1);
 
 s:=s+a[i,j]; 
 end;
assign(f2, 'flip.out');
rewrite(f2);
writeln(f2, s);
close(f2);

end.