======================================================================

Pre-warm up

See "Rosetta Code"

======================================================================

Warm up
1) The recursion
a) implement a function calculating the factorial (two versions: 
recursive and iterative function, see the lecture)
https://en.wikipedia.org/wiki/Factorial

b) implement function calculating Fibonaci numbers (again, two versions: 
recursive and iterative)
https://en.wikipedia.org/wiki/Fibonacci_number#Generating_function

======================================================================
The main exercise: Backtracking

https://en.wikipedia.org/wiki/Backtracking

Implement: https://en.wikipedia.org/wiki/Eight_queens_puzzle

Write the program which will find all possible configurations (and count them)
of the queens on chess board (8x8).

The output should be:
Configuration: 1
 ABCDEFGH
1Q*******
2****Q***
3*******Q
4*****Q**
5**Q*****
6******Q*
7*Q******
8***Q****

Configuration: 2
 ABCDEFGH
1Q*******
2*****Q**
3*******Q
4**Q*****
5******Q*
6***Q****
7*Q******
8****Q***

....

Total number of possible configuratins: ??