var n,m,s:int64;
    i,q:longint;
begin
     assign(input,'sarpe.in');
     reset(input);
     assign(output,'sarpe.out');
     rewrite(output);
     readln(n);
     if n mod 2=1 then q:=1;
     s:=n*(n+1)div 2;
     if n mod 2=1 then s:=s-((n div 2+1)*(n div 2+2))div 2
     else s:=s-(n div 2*(n div 2+1))div 2;
     s:=s*4;
     if q=1 then s:=s+(n div 2+1)*2;
     writeln(s);



close(output);
end.