You are given an array of $n$ integers. Your task is to count the number of non-empty subsets of the given array with average equal to $a$ .
The first line has two integers $n$ and $a$ : the size of the array and the target average.
The next line has $n$ integers $x_1, x_2,\dots, x_n$ : the contents of the array.
Print one integer: the number of non-empty subsets with average equal to $a$ , modulo $10^9 + 7$ .