Program mencari kelipatan (Pascal)

program kelipatan; uses wincrt; var i,a: integer; coba: char; begin coba:='y'; while coba ='y' do begin a:=3; for i:=1 to 10 do begin write(a,' '); a:=a+3; end; write('coba program lagi?[y/t]');readln(coba); if coba ='t' then coba:='t'; end; readln; end.