add condition for the mathematical tasks

practica/stepik/stepik_tasks/README.md

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+# Stepik tasks
+Here you can find done tasks from stepik courses. 
+
+- [10_pass_100_break](10_pass_100_break.py) 
+
+    For each entered number, check: if the number is less than 10, then pass this number;
+if the number is greater than 100, then break;in other cases, print this number back to the console in a separate line.
+- [Counting_numbers](counting_numbers.py)
+
+    A program that reads numbers from input and after the first zero entered, prints the sum of the received numbers
+- [Intervals](intervals.py)
+
+    Write a program that takes an integer as input and prints True if the passed value falls within the interval (−15,12]∪(14,17)∪[19,+∞) and False otherwise (case matters)
+- [Percentage of letters](percentage_of_letters.py) 
+
+    - #1 Write a program that calculates the percentage of characters G (guanine) and C (cytosine) in an input string (the program should not be case sensitive)
+    - #2 Write a program that reads a string, encodes it using the proposed algorithm, and prints the encoded sequence to standard output. Encoding must be case sensitive
+- [Pie](pie.py)
+
+    Determine the area of the figure using the following input data:
+    1) **triangle**, a, b, c - lengths of the sides of the figure
+    2) **rectangle**, a, b - lengths of the sides of the figure
+    3) **circle**, r - radius of the circle
+- [Programmer's names](programmer_names.py)
+
+> Peculiarities of word endings in Russian, therefore the task is duplicated in Russian
+
+| English ver | Russian ver |
+|:-------------|:---------------|
+|Write a program that reads an integer from user inputn (non-negative), outputting this number to the console along with the word "programmer" correctly modified so that the robot can communicate normally with people, for example: 1 programmer, 2 programmers, 5 programmers| Напишите программу, считывающую с пользовательского ввода целое число n (неотрицательное), выводящее это число в консоль вместе с правильным образом изменённым словом "программист", для того, чтобы робот мог нормально общаться с людьми, например: 1 программист, 2 программиста, 5 программистов|
+
+- [Sum_num_from_last](sum_num_from_last.py)
+
+    A program that takes the left and right character from each character and combines them into one number. For the first and last numbers, the left and right numbers are the last and first numbers respectively
+- [Sum_num_nearby](sum_num_nearby.py)
+
+    A program that displays the sum of the right and left numbers from the main one. For the first and last numbers, the left and right numbers are the last and first numbers respectively
+- [Tickets](tickets.py)
+
+    A program that issues a “Lucky” or "regular" ticket, the number of which we entered. If all the numbers are the same - the ticket is lucky