Time Limit: 1s, Memory Limit: 32MB
Crud! Damian is late for a scouts camp but has yet to pack his socks.
As he likes to wear matching socks, he needs K socks of the same kind.
However, his socks (of N different kinds) are all in a jumble so he decides to just grab a handful of them.
Furthermore, he knows that he has A_i socks of type i.
How many socks does he need to grab to guarantee that he will have at least K socks of one kind?
The first line contains two integers, N and K.
The second line contains N space-separated integers, representing the contents of A.
A single integer representing the minimum number of socks that Damian has to grab.
If it is not possible for Damian to guarantee at least K socks, output -1 instead.
Subtask 1 (30%): 1 ≤ N ≤ 100; 0 ≤ K ≤ A_i ≤ 1000.
Subtask 2 (70%): 1 ≤ N ≤ 100; 0 ≤ A_i ≤ 1000; 0 ≤ K ≤ 1000.
Subtask 3 (0%): Sample Testcase.
5 5 5