Fast Postman#1552
A postman has to deliver several letters along a street. For each letter, he knows the delivery address (the number of meters from the left end of the street to the destination) and the maximum allowed time to deliver it. The postman moves at meter per second and delivers a letter instantly upon reaching its address. Determine whether it is possible to deliver all letters within the given constraints. If it is possible, find the minimum time required to deliver all of them.
The input consists of multiple test cases, each consisting of three lines.
The first line of each test contains two numbers: the number of addresses AddrNum~(1 \le AddrNum \le 50) and the postman's initial position initialPos~(1 \le initialPos \le 10^6), both in the same units as the addresses.
The second and third lines each contain AddrNum numbers. The -th number in the second line gives the address of the -th letter. The -th number in the third line gives the maximum allowed delivery time for the -th letter.
Each address is between and 10^6 inclusive. Each maximum time is between and 10^9 inclusive.
For each test case, print on a separate line the minimum time needed to deliver all letters within the given constraints, or if it is impossible.
Example 1