Inspired by [this glove-themed 538 Riddler Express Puzzle](https://fivethirtyeight.com/features/can-you-get-the-gloves-out-of-the-box/).

## Task
You are given a positive integer `n`, and a list `A = [a_1, a_2, ..., a_k]` of `k` distinct positive integers.

Then a restricted composition is an ordered list `P = [p_1, p_2, ..., p_m]` where each `p_i` is a (not necessarily distinct) member of `A`, and `p_1 + p_2 + ... + p_m = n`.

So, if `n = 10`, and `A = [2,3,4]` then an example of a restricted composition would be `P = [3,4,3]`. Another example would be `P = [2,3,3,2]`. A third example would be `P = [3,3,4]`. But there's no restricted composition that starts `[3,3,3,...]`, because `10-(3+3+3) = 1`, which is not in `A`.

We want the total number of different restricted compositions given the inputs, as an integer. 

## Inputs

A positive integer `n` and a list `A` of distinct positive integers. All reasonable input formats allowed.

## Output

The number of distinct restricted compositions.

## Terms and Conditions

This is [tag:code-golf]; and thus we seek the shortest submissions in bytes satisfying the constraints. Any use of the usual loopholes voids this contract.

## Test Cases

 (5, [2, 3, 4]) => 2
 (10, [2, 3, 4]) => 17
 (15, [3, 5, 7]) => 8