var a:array[1..16,1..16] of -1000000..1000000;
f:text; i,j,n,m:1..16; s:longint;
begin
assign(f,'flip.in'); reset(f); read(f,n); readln(f,m);
for i:=1 to n do begin
    for j:=1 to m do
        read(f,a[i,j]);
    readln(f); end; close(f);
for i:=1 to n do begin
    s:=0;
    for j:=1 to m do
        s:=s+a[i,j];
    if s<0 then for j:=1 to m do a[i,j]:=-a[i,j];
    end;
for j:=1 to m do begin
    s:=0;
    for i:=1 to n do
        s:=s+a[i,j];
    if s<0 then for i:=1 to n do a[i,j]:=-a[i,j];
         end;
s:=0;
assign(f,'flip.out');rewrite(f);
for i:=1 to n do
    for j:=1 to m do
       s:=s+a[i,j];
write(f,s);close(f); end.