C++ multiset automatically sort person objects stored by pointer

#include <iostream>
#include <set>
#pragma warning (disable:4786)//from   w w  w. j a va  2  s.c o  m
#include <string>
using namespace std;
class person
{
   private:
   string lastName;
   string firstName;
   long phoneNumber;
   public:
   person() :             // default constructor
   lastName("blank"), firstName("blank"), phoneNumber(0L)
   {  }
   // 3-arg constructor
   person(string lana, string fina, long pho) :
   lastName(lana), firstName(fina), phoneNumber(pho)
   {  }
   friend bool operator<(const person&, const person&);
   void display() const   // display person's data
   {
      cout << endl << lastName << ",\t" << firstName
      << "\t\tPhone: " << phoneNumber;
   }
   long get_phone() const // return phone number
   { return phoneNumber; }
}; //end class person
// overloaded < for person class
bool operator<(const person& p1, const person& p2)
{
   if(p1.lastName == p2.lastName)
      return (p1.firstName < p2.firstName) ? true : false;
   return (p1.lastName < p2.lastName) ? true : false;
}
// function object to compare persons using pointers
class comparePersons
{
   public:
   bool operator() (const person* ptrP1,
   const person* ptrP2) const
   { return *ptrP1 < *ptrP2; }
};
int main()
{                          // a multiset of ptrs to persons
    multiset<person*, comparePersons> setPtrsPers;
    multiset<person*, comparePersons>::iterator iter;
    //make persons
    person* ptrP1 = new person("K", "B", 4);
    person* ptrP2 = new person("M", "S", 3);
    person* ptrP3 = new person("D", "W", 8);
    person* ptrP4 = new person("W", "J", 9);
    person* ptrP5 = new person("B", "P", 6);
    person* ptrP6 = new person("M", "A", 8);
    person* ptrP7 = new person("F", "R", 7);
    person* ptrP8 = new person("M", "S", 7);
    setPtrsPers.insert(ptrP1);         //put persons in multiset
    setPtrsPers.insert(ptrP2);
    setPtrsPers.insert(ptrP3);
    setPtrsPers.insert(ptrP4);
    setPtrsPers.insert(ptrP5);
    setPtrsPers.insert(ptrP6);
    setPtrsPers.insert(ptrP7);
    setPtrsPers.insert(ptrP8);
    //display multiset
    cout << "\n\nSet sorted when created:";
    for(iter=setPtrsPers.begin(); iter != setPtrsPers.end(); iter++ )
       (**iter).display();
    iter = setPtrsPers.begin();         //delete all persons
    while( iter != setPtrsPers.end() )
    {
       delete *iter;                    //delete person
       setPtrsPers.erase(iter++);       //remove pointer
    }
    cout << endl;
    return 0;
}