Given a set of numbers, print out how many non-empty subsets sum to a given integer.
Input Format
The first line contains two integers N and S. The second line contains N space-separated integers a_1, a_2, ..., a_N.
1 <= N <= 20
-100 <= S <= 100
-1000 <= a_i <= 1000
Output Format
A single integer, the number of non-empty subsets which sum to S. Two subsets are different if an element appears in one and does not appear in the other. Note that a_1 is distinct from a_2, even if their values are identical.