Most common letter
Problem
The input of the program is English text ending with a dot (there are no other “.” characters in the text). It is required to write a program that will determine and display the English letter that occurs most often in this text, and the number of such letters there. Lowercase and uppercase letters are considered indistinguishable. If there are several searched letters, then the program should display the first of them in alphabetical order.
For example, suppose the file contains the following entry:
It is not a simple task. Yes!
The most common letters are I, S and T (the word Yes is not included in the calculation, as it is located after the period). Therefore, in this case, the program should output two characters separated by a space: I 3