Why is the copy constructor used instead of the assignment operator?

Question

Here's how it is defined MyClass:

class MyClass {
    double x, y;
    public:
        MyClass (double a = 0., double b = 0.) {
            x = a;
            y = b;
            cout << "Using the default constructor" << endl;
        }
        MyClass (const MyClass& p) {
            x = p.x;
            y = p.y;
            cout << "Using the copy constructor" << endl;
        }
        MyClass operator =(const MyClass& p) {
            x = p.x;
            y = p.y;
            cout << "Using the assignment operator" << endl;
            return *this;
        }
};

And I tested when every constructor or method is called in my main program:

int main() {
    cout << "MyClass p" << endl; MyClass p; cout << endl;
    cout << "MyClass r(3.4)" << endl; MyClass r(3.4); cout << endl;
    cout << "MyClass s(r)" << endl; MyClass s(r); cout << endl;
    cout << "MyClass u = s" << endl; MyClass u = s; cout << endl;
    cout << "s = p" << endl; s = p; cout << endl;
}

Why is the copy constructor used in the fourth example MyClass u = sinstead of the assignment operator?

EDIT

Including output as given:

MyClass p
Using the default constructor

MyClass r(3.4)
Using the default constructor

MyClass s(r)
Using the copy constructor

MyClass u = s
Using the copy constructor

s = p
Using the assignment operator
Using the copy constructor

Answer 1

, u . , . , , , . , , ++.

Answer 2

, . = ctor.