member function calling in "cout"

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C++

This is a simple code to understand classes, the code is working good unless i call getlastname function.. if this function have nothing to do then why we write this getfirsttname and getlastname functions .. ???
here is my code please have eye ..
i want to call the get last name function,, but this will generate errors ..
i really need your comments here ..

Thank you For Your Consideration .. !!!!

#include <iostream>
#include <string>
using namespace std;
class personType
{
public:
	void print() const;
	void setName(string first, string last);
	string getFirstName() const;
	string getLastName() ; //  const is removed from here. !!
	personType(string first, string last);
	personType();
private:
	string firstName, lastName;
};
void personType::print() const
{
	cout << firstName << " " << lastName;
}

void personType::setName(string first, string last)
{
	firstName = first;
	lastName = last;
}

string personType::getFirstName() const
{
	return firstName;
}

string personType::getLastName() 
{
	return lastName;
}

// Here Comes The Constructor Turn
personType::personType(string first, string last)
{
	firstName = first;
	lastName = last;
}
int main()
{
	personType p;
	p.setName("Nerdy", "Usman");
	p.print();
	cout << p.getLastName();	// What The heck. ?!
	system("pause");
	return 0;
}