请注意，数据为10^7，你用cin读入很容易超时的！
by wjcxr @ 2016-12-17 22:41:04
最好用scanf读入，比较快的，应该不会超时
by wjcxr @ 2016-12-17 22:42:40
long long a[1000000],b[1000000];
by XiaoShenKeDeJiuSh @ 2017-01-18 10:50:57
数组太多
by XiaoShenKeDeJiuSh @ 2017-01-18 10:51:39
和阳光天蝎想法一致
by 机智如猴 @ 2017-01-18 11:06:49
读入优化
by McGrady @ 2017-01-24 20:48:12