说明：  1. 野人与传教士过河问题：有传教士和野人各三人需要过河，他们都会划船。现只有一条船，一次只能载两人。假设野人多于传教士时传教士就会被吃掉。编程求出所有能确保全部安全的过河的计划，并给出Visual Prolog程序
(1. Savage and missionaries across the river problem: There are three missionaries and savages the need to cross the river, they will be boating. Now only one boat, one can only to two. Assuming more than savages missionaries missionaries will be eaten. Find all programming to ensure the safety of all plans across the river, and gives Visual Prolog program)