MovConstrAssign4, C++ (gcc)

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//g++  7.4.0

////////////////////////////////////////////////////////////////////////////
//MovConstrAssign4: understanding Move constructor and assignment using move semantics
//this code is created by Rezaul Hoque on July 01,2022;
//contact:jewelmrh@yahoo.com;Dhaka,Bangladesh;https://rezaulhoque.wordpress.com,https://hoquestake.blogspot.com
//note: codes shared by Rezaul Hoque on rextester are not for sale; they are created and shared to facilitate the algorithm learning process; many like Hoque use this platform to practice programming ;Rezaul hopes his contribution helps others to fine tune their learning;
//////////////////////////////////////////////////////////////////////////////
#include <iostream>
#include <string>
class C{
std::string s;
public:
C(std::string a){s=a;}

C(C& c){std::cout<<"Copy constructor in work\n";
s=c.s;}
~C(){}
std::string getS(){return s;}
};
class M{

std::string m;

public:
M(std::string z="Hi\n"){
 m=z;}
M(const M& c){m=c.m; std::cout<<"Move construction failed. Copy constructor in work\n";}
M(M&& ot
){
std::cout<<"Move constructor in work\n";
m=std::move(ot.m);

}
M& operator=(M&& ot)
{
if (this != &ot)
{

m=std::move(ot.m);

}
std::cout<<"Move assignment is in work\n";
return * this;
}
std::string getM(){ return  m;}
};
M getStr(M a){

return a;
}
class N :public M{
public: 
std::string n;
};
class O: public N{
public:
~O(){}//destructor blocks implicit move constructor and assignment
};
class P : public N{
public:
std::string p;
};
int main()
{
C a("hi\n");
std::cout<<a.getS();
//Move constructor
M z=getStr(M());
std::cout<<z.getM();

std::cout<<"After move:\n";
std::cout<<z.getM();
//Move assignment operator
M g("there\n");
std::cout<<"Before move constructor: \n";
std::cout<<g.getM();
std::cout<<"After move constructor: \n";
g=getStr(M());
std::cout<<g.getM();
N n1;
std::cout<<"Before move semantics: \n";
std::cout<<"n1.getM() :";
std::cout<<n1.getM();

N n2=std::move(n1);

std::cout<<"After move constructor: \n";
std::cout<<"n1.getM() :";
std::cout<<n1.getM();
std::cout<<"\nn2.getM() :";
std::cout<<n2.getM();
O o1;
O o2=std::move(o1);

return 0;
}

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Compilation time: 0.52 sec, absolute running time: 0.15 sec, cpu time: 0.01 sec, memory peak: 5 Mb, absolute service time: 0,84 sec