#include <iostream>
#include <string>

using namespace std;

class SillyString{
    public:
        SillyString()=default;
        SillyString(string s):word(s){};

        SillyString & operator = (const SillyString & other) {
           word = other.word;
           return *this;
        }

        SillyString &  operator +(const SillyString  & other) {
           SillyString newOne(word + "," + other.word);
           return newOne;
        }

        friend ostream & operator << (ostream & s, const SillyString & other);

    private:
        string word;
};

ostream & operator << (ostream & s, const SillyString & other){
     s << other.word;
     return s;
}

int main() {
    SillyString a("hello");
    SillyString b("world");

    SillyString c;

    cout << " a = " << a << "  b = " << b << endl;
    c = a + b;

    cout << " c = " << c << endl;
 
    return 0;
}