Stack of number V2

#include <iostream>
using namespace std;

struct Sstack
{
    int key;
    Sstack* next;
}*start = NULL;

struct Pstack
{
    int key;
    Pstack* next;
}*start2 = NULL;

void addElement(unsigned int& countOfNumber)
{
    Sstack* s;
    s = start;
    int Snum;
    do
    {
        cout << "Enter Positive Number: ";
        cin >> Snum;

    } while (Snum < 0);


    start = new Sstack;

    start->key = Snum;
    start->next = s;

    countOfNumber++;


    cout << "Element added" << endl;

    cout << endl;
}

void addElementToP(unsigned int& countOfNumber, unsigned int n)
{
    Pstack* s;
    s = start2;


    start2 = new Pstack;

    start2->key = n;
    start2->next = s;

    countOfNumber++;


    cout << "Element added" << endl;

    cout << endl;
}

void removeElement(bool isP)
{

    if (isP) {


        while (start2)
        {

            Pstack* s = start2;

            bool isLast = false;

            do
            {
                if (!s->next) {

                    isLast = true;
                    break;

                }

                if (s->next != start2) {
                    s = s->next;
                }

            } while (s->next != start2);

            if (isLast)
            {
                start2 = NULL;

                delete s;

            }
            else {
                start2 = s;

                delete s;
            }
        }


    }
    else {


        while (start)
        {

            Sstack* s = start;

            bool isLast = false;

            do
            {
                if (!s->next) {

                    isLast = true;
                    break;

                }

                if (s->next != start) {
                    s = s->next;
                }

            } while (s->next != start);


            if (isLast)
            {
                start = NULL;

                delete s;

            }
            else {
                start = s;

                delete s;


                start->next = NULL;
            }

        }


        cout << "Element/s removed\n";

    }

}

void printElements()
{
    Sstack* s = start;

    while (s)
    {
        cout << s->key << " ";

        s = s->next;
    }

    cout << endl;

    if (start2)
    {
        Pstack* s2 = start2;

        while (s2)
        {
            cout << s2->key << " ";

            s2 = s2->next;
        }
    }

    cout << endl;
}

void sortElementInPStack(unsigned int countOfNumber)
{
    unsigned int count = 0;

    Sstack* s = start;

    int smallest = s->key;

    s = s->next;

    removeElement(true);

    while (count < countOfNumber)
    {
        for (int i = count + 1; i < countOfNumber; i++)
        {
            if (smallest > s->key)
            {
                smallest = s->key;
            }

            s = s->next;
        }

        addElementToP(count, smallest);

        s = start;

        if (count < countOfNumber)
        {
            for (int i = 0; i < count; i++)
            {
                s = s->next;
            }

            smallest = s->key;
        }




    }




}

int main()
{
    short choice;

    unsigned int countOfNumber = 0;

    do
    {
        cout << "[1] Add element\n[2] Remove element \n[3] Print elements\n[4] Sort by descending order\n[0] Exit\n";
        cin >> choice;

        switch (choice)
        {
        case 1:
            system("cls");

            addElement(countOfNumber);

            choice = -1;

            break;
        case 2:

            system("cls");

            if (!start) {
                cout << "No elements to remove\n";
            }
            else {
                removeElement(false);
            }


            choice = -1;

            break;

        case 3:

            system("cls");

            if (!start) {
                cout << "No elements to print\n";
            }
            else {
                printElements();
            }

            choice = -1;

            break;

        case 4:

            system("cls");


            if (!start) {
                cout << "No elements to sort\n";
            }
            else {

                if (countOfNumber > 1) {
                    sortElementInPStack(countOfNumber);

                }
                else {
                    cout << "Only one element\n";
                }

            }

            choice = -1;

            break;
        default:
            break;
        }

    } while (choice < 0 || choice > 4);


}