Character Frequency Analysis

You are given a list of strings. Your task is to compute the frequency of each alphabetical character across all strings. Note that:

• The comparison is case-insensitive; that is, 'A' and 'a' are considered the same.
• Only alphabetic characters (a-z and A-Z) should be counted; ignore digits, punctuation, and whitespace.

The output should be a JSON formatted dictionary with keys sorted in lexicographical order. Use LaTeX formatting for any formulas if needed. For example, if the input string is hello, then the output should be:
{"e":1,"h":1,"l":2,"o":1}

inputFormat

The first line of input contains an integer n denoting the number of strings. Each of the following n lines contains a string.

For example:

3
hello
world
leetcode

outputFormat

Output a single line: a JSON dictionary representing the frequency of each alphabetical character (all in lowercase), with keys in lexicographical order. For example, for the sample input above, the output should be:

{"c":1,"d":2,"e":4,"h":1,"l":4,"o":3,"r":1,"t":1,"w":1}

1
hello

{"e":1,"h":1,"l":2,"o":1}