program to print the serie 0, 1, 1, 2, 3. 5, 8. 13, 21

int main()
{
    char ch = 'y';
    int x = 0, y = 1, z = 0;
    while (ch == 'y' || ch == 'Y')
    {
        cout << x;
        z = x + y;
        x = y;
        y = z;
        cout << ", ";
        cin >> ch;
    }
    return 0;
}