You are given a 0-indexed array of strings called strings.

Define a boolean function isPrefixAndSuffix that takes two strings, s1 and s2:

isPrefixAndSuffix(s1, s2) returns true if s1 is both a starting substring (prefix) and an ending substring (suffix) of s2, and false otherwise.

For example, isPrefixAndSuffix("cat", "cattacat") is true because "cat" is both a starting and ending substring of "cattacat", but isPrefixAndSuffix("dog", "doghouse") is false.

Return the count of all index pairs (i, j) such that i < j and isPrefixAndSuffix(strings[i], strings[j]) is true.

A prefix of a string is a substring that appears at the start, beginning from index 0.

A suffix of a string is a substring that appears at the end, finishing at the last character.

Example 1:

Input: strings = ["d","dad","dadbestdad","dd"]
Output: 4
Explanation: In this example, the counted index pairs are:
i = 0 and j = 1 because isPrefixAndSuffix("d", "dad") is true.
i = 0 and j = 2 because isPrefixAndSuffix("d", "dadbestdad") is true.
i = 0 and j = 3 because isPrefixAndSuffix("d", "dd") is true.
i = 1 and j = 2 because isPrefixAndSuffix("dad", "dadbestdad") is true.
Therefore, the answer is 4

Example 2:

Input: strings = ["abc", "abcd", "xyz", "xyzxyz"]
Output: 1
Explanation:
The only valid index pair is:
(2, 3): isPrefixAndSuffix("xyz", "xyzxyz") is true. So, the answer is 1.

Example 3:

Input: strings = ["test", "exam"]
Output: 0
Explanation: No pairs meet the condition, so the result is 0.

Constraints

1 <= strings.length <= 50

1 <= strings[i].length <= 10

strings[i] consists only of lowercase English letters.

68. Count Prefix and Suffix Pairs