Complex sentence: If the opponent takes 3 marbles, the first player should take 1, if the opponent takes 2 marbles, the first player should take 2, and finally if the opponent takes 1 marbles, the first player should take 3.
Split into simpler sentences: If the opponent takes 2 marbles, the first player should take 2. Finally, if the opponent takes 1 marble, the first player should take 3.