Distinct Values Subsequences

Given an array of n integers, count the number of subsequences where each element is distinct. A subsequence is a sequence of array elements from left to right that may have gaps. Input The first line has an integer n: the array size. The second line has n integers x_1,x_2,\dots,x_n: the array contents. Output Print the number of subsequences with distinct elements. The answer can be large,