How to add up a die roll using user inputted number of die and sides of die in C++?

I'm having trouble with my die roller program not staying within its user-set parameters when it rolls a die. The program is to:

• be able to take an input in for form nDx or ndx where the d is the letter d or D.

• n may or not be present. If it is, it represents the number of dice. If not, assume it is a 1.

• x may or may not be present. If it is, it represents the number of sides on the die. If it is absent, assume it is a 6.

• If n is absent, x must be present. If x is absent, n must be present.

• Remember, you need to roll each die individually and then add up the values. Also show the individual dice if n > 1.

• For example: 2d means roll 2 six-sided dice (2d6). d20 means roll one 20-sided die (1d20)

An example of my output I receive is:

• Enter number of die being used:
• 4
• Enter the number of sides:
• 5
• results are:
• 4d5 = 3
• 7
• 11
• 13
• 13 ----jGRASP: operation complete.

What I need is the output to be like this:

• input dice code: 3d6

• 3d6 = 4 + 2 + 5 = 11

I'm terribly bad at coding this, so please go easy on me. This is what I currently have:

#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

int dice (int nrDice, int nrSides)
{
   int result = 0;
   for (int i = 0; i < nrDice; i++)
   {
      result += ((rand()% nrSides) + 1);
      cout << result << endl;
   }

   return result;
}

int main ()
{  
   int nrDice = 1, nrSides;
   srand(time(0));

   cout << "Enter number of die being used: " << endl;
   cin >> nrDice;

   cout << "Enter the number of sides: " << endl;
   cin >> nrSides;

   cout << nrDice << "d" << nrSides << " = " << dice (nrDice, nrSides) << endl;

   return 0;
}