You are given an array of strings `words` and a string `pref`.

Return the number of strings in `words` that contain `pref` as a prefix.

A prefix of a string `s` is any leading contiguous substring of `s`.

Example 1:

    Input: words = ["pay","attention","practice","attend"], pref = "at"
    Output: 2
    Explanation: The 2 strings that contain "at" as a prefix are: "attention" and "attend".

Example 2:

    Input: words = ["leetcode","win","loops","success"], pref = "code"
    Output: 0
    Explanation: There are no strings that contain "code" as a prefix.

Constraints:

- `1 <= words.length <= 100`
- `1 <= words[i].length, pref.length <= 100`
- `words[i]` and `pref` consist of lowercase English letters.