on right click on villager:
    cancel event
    if name of the clicked entity is "&7Kowal":
    	if player's tool is book named "&3Ulepszenie 1":
        	chance of 70%:
            	remove 1 book named "&3Ulepszenie 1" from player
                give player 1 book named "&3Ulepszenie 1" 
            chance of 30%:
            	remove 1 book named "&3Ulepszenie 1" from player
                send "&6Uhh.. &eCos spaliles"