#include <iostream>
using namespace std;
class Base {
public:
    int a = 1;
protected:
    int b = 2;
private:
    int c = 3;
};
class Derived : protected Base {
public:
    void func() {
        // 派生类成员函数内部
    }
};
int main() {
    Derived d;
    return 0;
}