var f,g:text;
i,j,nr,n:longint;
aux:char;
a:array[1..10000] of char;
begin
assign(f,'nunta.in'); reset(f);
assign(g,'nunta.out'); rewrite(g);
readln(f,n);
if n mod 2 = 1 then writeln(g,n) else writeln(g,n+1);
close(f);
close(g);
end.