Inaninamate masculine genitive in a in West Slavic languages

I've noticed that among Polish, Slovak, and Czech, Polish has the most instances of an inanimate masculine genitive in a, followed by Slovak and then by Czech. Nevertheless, I've discovered a Czech word with an inanimate masculine genitive in a, but with a u in Polish and Slovak. It is Czech ocet (vinegar), genitive singular octa. Slovak ocot and Polish ocet have octu in the genitive singular.