Dreadful Deadlines#303
Contrary to popular belief, diligence does not always pay off! Over his years at Stanford, David found that, despite his best efforts, work would always expand to fill the available time. To improve his daily productivity, David decided to master the art of procrastination.
David has assignments due next week. The -th assignment takes x_i units of time and must be finished by time t_i. David can only work on one assignment at a time, and once he begins an assignment, he must continue working on it until it is completed.
What is the latest time that David can start to ensure all deadlines are met?
The input file contains multiple test cases. Each test case consists of three lines. The first line contains a single integer (1 \le n \le 1000). The second line contains integers x_1, x_2, \ldots, x_n (1 \le x_i \le 10) separated by single spaces. The third line contains integers t_1, t_2, \ldots, t_n (1 \le t_i \le 1000) separated by single spaces.
A blank line separates input test cases, as in the sample input below. A single line containing 0 marks the end of input; do not process this case.
For each test case, output the latest integer time that David can start and still finish all assignments on time. If the latest start time is before time , print impossible.
Example 1