B'You are given a positive integer k . For a multiset of integers S , define f(S) as the following. More formally, let |S| denote the number of elements in S . Then, You are given a multiset of integers, A . Compute sum limits_{B subseteq A} f(B) modulo 10^9+7 . Note that in this problem, we distinguish the elements by indices instead of values. That is, a multiset consisting of n elements always has 2^n distinct subsets regardless of whether some of its elements are equal. The first line of input contains two integers n and k , where n is the number of elements in A ( 1 <= k <= n <= 600 ). The second line of input contains n integers a_1,a_2, ... ,a_n , describing the elements in A ( -10^9 <= a_i <= 10^9 ). Output sum limits_{B subseteq A} f(B) modulo 10^9+7 . Consider the first sample. From the definitions we know that So we should print (0+0+0+0-2-4+8+8) bmod (10^9+7)=10 . In the second example, note that although the multiset consists of three same values, it still has 8 distinct subsets: varnothing, {1 }, {1 }, {1 }, {1,1 }, {1,1 }, {1,1 }, {1,1,1 } . '...