Find the number of your Homework No.2 calculating the
expression: (Faculty_Number
% 21).

Your program must contain at least two functions - the main function
for input and output and the second function for solving the problem.

Write a program that

(0) reads a set of floating-point data values from the input, and prints out the average (mean) of the data (see Exercise 4.24).

(1) reads a set of strings and prints out the shortest of them.

(2) reads two natural numbers and prints out its greatest common divisor*.

(3) reads two natural numbers and prints out its least common multiple*.

(4) reads two strings and prints out true, if the second string is a substring of the first and false, otherwise.

(5) reads a positive number and prints out all its divisors.

(6) reads a positive number n and prints out all prime numbers, less than n.

(7) reads a set of words and prints them out in reverse order of their letters (for example "print" as "tnirp").

(8) reads a set of positive numbers and prints out their binary representations.

(9) reads a set of positive numbers and prints out their octal number base* system representations.

(10) reads a set of strings of ones and zeros and prints out the numbers (in decimal system), whose binary system* representations are these strings.

(11) reads a positive integer N and prints the sum of this number and the number generated by the digits of N in backward order.

(12) reads a natural number n and prints out the sum: 1 + 2.3 + 3.4.5 + 4.5.6.7 +...+ n.(n + 1)...(2n - 1).

(13) reads a natural number n and prints out the sum of the prime divisors of n.

(14) reads a word and prints out "YES", if it a palindrome*, i.e. a word, that reads the same backward or forward.

(15) reads two words and prints out "YES", if the second word is made by transposing the letters of the first word (anagram*).

(16) reads a string and prints out all repeating (at least twice) symbols in it.

(17) reads two positive integers a and b (a < b) and prints out the count of integer numbers in the interval [a,b], which have no the same digits (example: 120,123,124,125 in the interval [119,125]).

(18) reads a positive number n and prints out first n numbers (from the sequence 1,2,3,4,5,...) which are divisible* by 2, 3 and 5.

(19) reads two natural numbers a and b and prints out the number of digits of ab (the product of a and b).

(20) reads a positive number n and prints out a list of all perfect numbers* (are equal to the sum of all of their factors*), less than n.

Notes:

- The phrase "reads a set of" means processing a sequence of inputs, 4.6 from Chapter 4. Basic Control Flow.
- *Copy and paste the phrase in the Gooogle and hit SEARCH!