/**
*
* Solution to homework assignment 1
* Introduction to programming course
* Faculty of Mathematics and Informatics of Sofia University
* Winter semester 2019/2020
*
* @author <Velislava Petkova>
* @idnumber <62428>
* @task <3>
* @compiler <VC>
*
*/
#include<iostream>
#include <cmath>
using namespace std;

int convertNumber(char hexnum)                           //A function which converts out hex number to a dec number to operate with
{                                                        //We use the asce table to see if the user has written a number or a sybol and we convert it
	int decNum = 0;                                      //The value of our dec number is 0 at the beggining
	if ((int)hexnum >= 48 && (int)hexnum <= 57)           //If our input was a number from 0 to 9
	{
		int count = 48;                                   //This counter saves the value of the code of our input
		double dechelp = 0;                               //This variable saves the value of our dec number
		while ((int)hexnum != count)                      //If the code of our input is diggerent than the code we are checking with (count)
		{                                                 //we move to the next code (count++) and to a next number from 0 to 9
			count++;
			dechelp++;
		}
		decNum = dechelp;                                //The dec number we return is a digit from 0 to 9
	}
	if ((int)hexnum >= 65 && (int)hexnum <= 70)          //If the user's input was a letter
	{
		int count = 65;                                  //We proceed the same way but we start checking with the code ot the letter A and our first
		int dechelp = 10;                                //possible dec number is 10; If there isn't a match we move to B and 11 and so on
		while ((int)hexnum != count) {
			count++;
			dechelp++;
		}
		decNum = dechelp;
	}
	return decNum;                                       //We return our dec number to operate wth
}

char fromDecToHex(int num)
{
	char digit = ' ';

		switch (num)                      //We create a switch to turn a variable from an int to a char and when there is a match we return the char
		{
		case 0:
			digit = '0';
			return digit;
			break;
		case 1:
			digit = '1';
			return digit;
			break;
		case 2:
			digit = '2';
			return digit;
			break;
		case 3:
			digit = '3';
			return digit;
			break;
		case 4:
			digit = '4';
			return digit;
			break;
		case 5:
			digit = '5';
			return digit;
			break;
		case 6:
			digit = '6';
			return digit;
			break;
		case 7:
			digit = '7';
			return digit;
			break;
		case 8:
			digit = '8';
			return digit;
			break;
		case 9:
			digit = '9';
			return digit;
			break;
		case 10:
			digit = 'A';
			return digit;
			break;
		case 11:
			digit = 'B';
			return digit;
			break;
		case 12:
			digit = 'C';
			return digit;
			break;
		case 13:
			digit = 'D';
			return digit;
			break;
		case 14:
			digit = 'E';
			return digit;
			break;
		case 15:
			digit = 'F';
			return digit;
			break;

	}

}



int main()
{
	char num1 = ' ';
	char num2 = ' ';
	char operation = ' ';
	int result = 0;
	cout << "Input operation " << endl;
	cin.get(operation);                      //If the user's input is more than one symbol the program only takes one symbol
	cin.ignore();                            //So if we write a negative number it onlu takes the - and then when we
	cout << "Input first number " << endl;   //check if the input is from 0 to 9 or A to F it consuders it a wrong input
	cin.get(num1);
	cin.ignore();                              //Luybo said we can use this type of verification
	cout << "Input second number " << endl;
	cin.get(num2);
	cin.ignore();

	if (!cin)                                        //Checks if the input is somehow wrong
	{
		cout << "Wrong input!" << endl;
		return 1;
	}

	else
	{

		if ((int)num1 < 48 || ((int)num1 > 57 && (int)num1 < 65) || (int)num1>70)
		{
			cout << "Wrong input! " << endl;                                          //Checks if the input is in the right range
		}
		else if ((int)num2 < 48 || (int)num2>57 && (int)num2 < 65 || (int)num2>70)
		{
			cout << "Wrong input! " << endl;
		}
		else {
			int number1 = 0;
			int number2 = 0;

			number1 = convertNumber(num1);        //We call the function we use to convert our input from char to int
			number2 = convertNumber(num2);

			switch (operation)                        //A switch for the operation
			{
			case '+':
				result = number1 + number2;
				break;
			case '-':
				result = number1 - number2;
				break;
			case '*':
				result = number1 * number2;
				break;
			case '/':
				result = number1 / number2;
				break;
			case '%':
				result = number1 % number2;
				break;
			default:
				cout << "Wrong input of operation! " << endl;      //If the input of operation is not accurate it shows a message
				return 0;
			}
			int absResult = abs(result);                           //Takes the positive value of our result if it happens to be negative
			//int left = 0;
			int firstDigit = 0;
			int secondDigit = 0;

			secondDigit = absResult % 16;       //The first digit of our result we get when we divide by 16
			if ((absResult / 16) != 0) firstDigit = absResult / 16;

			if ((absResult / 16) != 0)                   //If what we have left from our result divided by 16 is diggerent than 0 that means our result has two
			{                                //digits when converted to hex
				                             //If it has 2 digits we save the value of the second one
				if (absResult != result)     //If we have a negative result we display the result with a -
				{
					cout << "-" << fromDecToHex(firstDigit) << fromDecToHex(secondDigit) << endl; //We call a function to convert the digits to hex
				}
				else
				{
					cout << fromDecToHex(firstDigit) << fromDecToHex(secondDigit) << endl;
				}

			}
			if ((absResult / 16) == 0)                             //If what is left from the number divided by 16 is 0 we only have one digit
			{                                          //and we proceed the same way as we did with 2 digits
				if (absResult != result)
				{
					cout << "-" << fromDecToHex(secondDigit) << endl;
				}
				else  cout << fromDecToHex(secondDigit) << endl;
			}
		}

	}
	return 0;
}