Homework
      
      [Basic Control Flow, Functions]
        
       
    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 sequence of floating-point data
      values from the input, and prints out the average (arithmetic
        mean) of the data (see Exercise 4.24).
      (1) reads a sequence of strings and
      prints out the longest of them.
    (2) reads a word and prints out "PALINDROME", if it a palindrome, i.e. a word, that reads the
      same backward or forward.
    (3) reads two natural
        numbers and prints out their greatest
        common divisor. 
      (4) reads two natural
        numbers and prints out their least
        common multiple. 
      (5) reads two strings
      and prints out yes,
      if the second string is a substring of
      the first and no,
      otherwise. 
      (6) reads a positive number n
      and prints out all prime numbers,
      less than or equal to n.
      (7) reads a positive integer N
      and prints the sum of this number and the number generated by the
      digits
      of N in backward order.
      
      (8) 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). 
      (9) reads a natural
        number n and
      prints out the sum of the prime divisors of n. 
      (10) reads two words and prints out "YES", if the second word is made by
      transposing the letters of the first word (anagram).
      (11) reads a string
      and prints out all repeating (at least twice) symbols in it.
    (12) reads a positive number and prints out all its divisors. 
    (13) 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. 
      (14) reads two natural
        numbers a and b and prints out the number
      of digits
      of ab (the product
      of a and b).
      (15) 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.
    (16) reads two strings and
      prints out "YES", if
      the second string contains only characters
      of the first string (example: "aaabb" and "a" - YES).
    (17) reads a sequenceof words and prints
      them out in reverse order of their letters
      (example: "print" as
      "tnirp"). 
      (18) reads a sequence of  positive
      numbers and prints out their binary
        numeral system representations (example: 3, 8 are
      represented by 11, 1000). 
      (19) reads a sequence of  positive
      numbers and prints out their octal number base system representations. 
    (20) 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:  in the interval [110,124] there are 3 such numbers
      - 120,123,124). 
    (21) reads a sequence of  strings of ones
      and zeros and prints out the numbers (in decimal system),
      whose binary
        system
      representations are these strings. 
      (22) reads two strings and
      prints out yes, if
      the second string is a prefix of the
      first and no,
      otherwise. 
      (23) reads two strings and
      prints out yes, if
      the second string is a subsequence of
      the first and no,
      otherwise. 
    (24) reads two strings and
      prints out yes, if
      the second string is a suffix of the
      first and no,
      otherwise. 
    
      Note: The phrase "reads a
        sequence of" means processing a sequence of inputs, see
      4.6 from Chapter 4. Basic Control
        Flow.