====== HW 02 - Calculator ======
The task is to write a simple program that performs the following basic integer arithmetic operations: addition, subtraction, multiplication and division.

You will get the operands from the standard input of your program as follows
<code>
<number of digits of the 1st operand>
<1st operand>
<operator +, -, *, />
<number of digits of the 2nd operand>
<2nd operand>
</code>

The operands can also be negative numbers starting with //-// (minus sign).

**The operands can also have more than 30 digits but less than 100 digits.** Thus, more than built-in types.

Your program is expected to print the result of the desired arithmetic operation on the standard output, and the return value shall be //0//.

However, there might be situations when an unsupported operation (meaning not one of the listed above) is entered.
In such situations, the program prints //Error: wrong operator// and returns //2//.
Also, any of the operands on the input might contain non-digit symbols, and those situations should result in printing //Error: wrong operands// and returning //3//.
In any other erroneous situation, print //Error: unknown error// and return //1//.

You can check your solution using Python, [[https://www.wolframalpha.com/|WolframAlpha]] or any other tool. No external library is allowed.

<note tip>
fgets() function allows flexible reading of stdin

getchar() reads a single character from stdin

You can find other possibly useful functions in [[https://en.cppreference.com/w/c/io|stdio.h]] library

Recall the variable-length array based on the user input from Lab02.
</note>

You can find testing instances <del>{{ :courses:be5b99cpl:hw:hw2_public.zip |here}}</del> {{ :courses:be5b99cpl:hw:hw2_public_v2.1.zip |here **UPDATED 2022-10-18 12:30**}}. Files with the suffix ''.in'' contain your input with ''.out'' your desired output.

<note tip>
When you have a file ''pub00.in'' containing the program input, you can pass it to your program in like
<code>
$ cat pub00.in | ./main
</code></note>

===== Examples =====
==== pub00 ====
^ Standard input ^ Expected output ^ Return value ^
| <code>
9
508983428
+
10
5303633367
</code> | <code>
5812616795
</code> | 0 |

==== pub03 ====
^ Standard input ^ Expected output ^ Return value ^
| <code>
25
1109945105925303633367189
-
13
5303633367189
</code> | <code>
1109945105920000000000000
</code> | 0 |

==== pub06 ====
^ Standard input ^ Expected output ^ Return value ^
| <code>
8
-53036333
*
55
-5089834282571709651070803999451059296045364409198455770
</code> | <code>
269946145925289289433504967492618198027807529912597563303491410
</code> | 0 |

==== pub07 ====
^ Standard input ^ Expected output ^ Return value ^
| <code>
19
7170965107080399945
/
10
-4505913015
</code> | <code>
-1591456623
</code> | 0 |

==== Faulty instances ====
^ Standard input ^ Expected output ^ Return value ^
| <code>
5
71709
a
10
-4505913015
</code> | <code>
Error: wrong operator
</code> | 2 |
| <code>
5
Hello
-
10
-4505913015
</code> | <code>
Error: wrong operands
</code> | 3 |
| <code>
5
71709
-
5
world
</code> | <code>
Error: wrong operands
</code> | 3 |

===== Evaluation =====
<note>
Upload your solution into [[https://cw.felk.cvut.cz/brute/|BRUTE]] as a zip archive containing only your program's source files.
This program will have to be simply compilable or provided with a Makefile or detailed description of the compilation process.
</note>
The maximum number of points is 10. No automatic evaluation, as you can test and verify your solution using the provided instances or generate your own.
  * 1 point - only small numbers
  * 3 points - addition and subtraction of large numbers
  * 3 points - multiplication of large numbers
  * 3 points - coding style (structured, commented, separated into functions etc.)

==== Bonus ====
  * 5 points - division of large numbers (only integer operation and the remainder is omitted)

==== Late submission ====
  * Submission is allowed one week after the deadline with the following <del>penalties</del> modifications:
    * <del>50% point reduction</del>
    * <del>It is not possible to use square brackets **arr[idx]** for array indexing.</del>
    * There will be only positive integers
    * Bonus will be only for half points (5 -> 2.5 points)
    * deadline on Saturday **22. 10.**
      * max 7.5 points
    * deadline on Tuesday **25. 10.**
      * either max 5 points OR max 7.5 points without using square brackets **arr[idx]** for array indexing