Exception thrown : Access violation reading location 0xCCCCCCCC

I'm a beginner in C++.
I should make program that outputs shape's area.

For example,

Input 1. Square  
Input 2. Rectangle  
Input 3. Circle  
Input 4. Print all the areas

User input: 1

Please give me the side.

The side is: 3

User input: 4

Square area: 9

//////////////////////////////////////////////////////

But there is problem about exception thrown.

I don't know why compiler indicates this.
Can someone explain this?

source.cpp:

using namespace std;

int main() {        
    const int n = 10;
    Shape * arr[n];

    int input, index = 0;

    do
    {
        cout << "What shape that you want to create?" << endl;
        cout << "Input 1. Square \n";
        cout << "Input 2. Rectangle \n";
        cout << "Input 3. Circle \n";
        cout << "Input 4. Print all the areas \n";
        cout << "Input -1. Exit \n";

        cout << "User input: ";
        cin >> input;

        //Use switch statement to check user's input
        switch (input)
        {
        case -1:
            cout << "You inputted number : -1 \n" << "The program will be ended. " << endl;
            break;
        case 1:
            double side;
            cout << "Please give me the side: ";
            cin >> side;

            arr[index] = new Square(side);
            index++;
            break;
        case 2:
            double width, length;
            cout << "Please give me the width and length \n";
            cout << "Width is: ";
            cin >> width;
            cout << "Length is: ";
            cin >> length;

            arr[index] = new Rectangle(width, length);
            index++;
            break;
        case 3:
            double radius;
            cout << "Please give me the radius: ";
            cin >> radius;

            arr[index] = new Circle(radius);
            index++;
            break;
        case 4:
            for (int i = 0; i < 10; i++)
            {
                cout << arr[i]->getName();
                cout << " area: ";

                cout << fixed << showpoint <<
                    setprecision(2);

                cout << arr[i]->area() << endl;
            }
            break;
        default:
            cout << "You entered different number mentioned above!" << endl;
        }
    } while (input != -1);

    delete[] arr;

    system("pause");
    return 0;
}

The compiler shows that Exception thrown at 0x0130C213 in Project.exe: 0xC0000005: Access violation reading location 0xCCCCCCCC.

I don't understand why the compiler shows this.

Please give me any advice!