Why is the size of class E 24 bytes in c++

Question

#include <iostream>
using namespace std;
class A{
public:
 int a;
};
class B: virtual public A{};
class C: virtual public A{};

 
class X{
public:
 int c;
};

class D: public B, public C{
};

class E: public D, virtual public X{
};
class F:virtual public X{
};
int main() {
 cout <<sizeof (E) << endl;
 return 0;
}

b inherits a,c inherits a,d inherits b and c，e inherits d and x Why is the size of class E 24 bytes in c++ GCC+MinGW-w64 compiler for Windows