var n,s,i:longint;
    f,g:text;
begin
     assign(f,'fractii.in');
     assign(g,'fractii.out');
     reset(f);
     rewrite(g);
     read(f,n);
     if n div 2=0 then s:=n+(n*n div 4)
                  else s:=n+((n-1)*(n-1))div 4;
     for i:=1 to n do
         If i mod 2=1 then s:=s+n div i;
     write(g,s);
     close(f);
     close(g);
end.