1、http://acm.pku.edu.cn/JudgeOnline/problem?id=14742、http://acm.pku.edu.cn/JudgeOnline/problem?id=27943、http://acm.pku.edu.cn/JudgeOnline/problem?id=13664、http://acm.pku.edu.cn/JudgeOnline/problem?id=13925、http://acm.pku.edu.cn/JudgeOnline/problem?id=2169
6、http://acm.pku.edu.cn/JudgeOnline/problem?id=31507、http://acm.pku.edu.cn/JudgeOnline/problem?id=14008、http://acm.pku.edu.cn/JudgeOnline/problem?id=20659、http://acm.pku.edu.cn/JudgeOnline/problem?id=186010、http://acm.pku.edu.cn/JudgeOnline/problem?id=2168
11、http://acm.pku.edu.cn/JudgeOnline/problem?id=279112、http://acm.pku.edu.cn/JudgeOnline/problem?id=253213、http://acm.pku.edu.cn/JudgeOnline/problem?id=171214、http://acm.pku.edu.cn/JudgeOnline/problem?id=170915、http://acm.pku.edu.cn/JudgeOnline/problem?id=1457
16、http://acm.pku.edu.cn/JudgeOnline/problem?id=113417、http://acm.pku.edu.cn/JudgeOnline/problem?id=113718、http://acm.pku.edu.cn/JudgeOnline/problem?id=1481