Three Zen monks go into a cave

Three Zen monks go into a cave to meditate....A couple of weeks later, a sound is heard outside the cave,.....A month later one of the monks says; "Did you hear that noise? I think it was a goat"....Three months later a second monk replies: "That wasn't a goat, it was a cow".....Six months later, the third monk says: "If you two are going to argue, I'm leaving!"