I'm trying to visit Krakow from the Czech Republic. I can get a train from Bohumin (CZ), which I'd like to buy a ticket to in advance. I'm looking at https://bilet.intercity.pl, where I can finfd the train I wanna take, but it says there's no option to buy a ticket? Does that mean it's fully sold out already? Doesn't seem to be, as I can buy it from the Czech Railways company at https://www.cd.cz, ut I'd like to check the Polish system as it's usually cheaper to buy there.