Required Mathematical Intelligence

Chapter 113 How to Cross the River
One person takes cats, chickens, and rice to cross the river. In addition to needing people to row, the boat can carry at least one of the three cats, chickens, and rice. When the person is not present, the cat wants to eat chicken, and the chicken needs to eat rice.Try to design a safe river crossing plan and minimize the number of ferry boats.

[Answer: 1 Take the chicken and come back empty-handed
2 Take the cat and bring the chicken back
3 Take rice and come back empty-handed
4 bring the chicken over]
(End of this chapter)