var n,i,j,p,q,r,tu:longint;
    f1,f2:text;
begin
assign(f1,'fractii.in'); reset(f1);
assign(f2,'fractii.out'); rewrite(f2);
read(f1,n);
if n=1 then write(f2,'1');
if n=2 then write(f2,'3');
if n>=3 then
   write(f1,n*n-2*(n div 2));
{for i:=1 to n do
    for j:=1 to n do
        begin
             p:=i;
             q:=j;
             r:=p mod q;
             while r<>0 do
                   begin
                        p:=q;
                        q:=r;
                        r:=p mod q;
                   end;
             if q=1 then inc(tu);
        end;
write(f2,tu);  }
close(f1);
close(f2);
end.