====== Homework 1 ======

==== Basics ====

A first homework to practice the basics from the first two labs; definition of variables, vectors, matrices, functions, working with strings and data structures.

Your task is to define the variables and functions as described below.

==== Your Task ====

Define the following objects as described in the {{template_01.jl|template}};
  * variables ''x'', ''y'', ''s'', and ''δ''
  * vectors ''primes'' and ''fives''
  * tuple ''tup''
  * matrices ''A'', ''B'' and 3D tensor ''C''

Implement the following two functions as described in the {{template_01.jl|template}};
  * The function ''normal'' for the calculation of the probability density value of the Normal distribution.
  * The functions ''count_letters'' for counting letters in text.

**Tips for successful solution:**
  * Define all objects (variables and functions) directly in the global scope of the submitted file "hw.jl". (Don't enclose them into modules or into other functions.)
  * When defining variables, check that the data type is correct, including a correct type of the elements in case of data structures.
  *   * Funkce ''count_letters'' by měla správně spočítat i písmena s nulovou četností. Stačí počítat písmena anglické abecedy. Počítejte velká a malá písmena dohromady a do slovníku indexujte malými písmeny.
  * The function ''count_letters'' should correctly count letters with zero occurrences as well. Count uppercase and lowercase letters together. Index into the dictionary using lowercase letters.
  * Don't import disallowed packages.
  * (You can write ''δ'' in VSCode by typing "\delta" and hitting tab. Or just copy it.)