Sao code dưới đây không xuất ra được danh sách thí sinh A,B?

#pragma once
#include<iostream>
#include <string>
using namespace std;
class Bngay
{
private:
 int ngay, thang,nam;

public:
	friend istream&operator>>(istream&is,Bngay &a);
	friend ostream&operator<<(ostream&os,Bngay a);

	
};
class thisinh
{
protected:
	string SBD;
	string hoten;
	Bngay ngaysinh;
	float tongdiem;
public:
	friend istream&operator>>(istream&is,thisinh &d);
	friend ostream&operator<<(ostream&os,thisinh d);
};


class thsinhB: public thisinh 
{
private:
	float van,su ,dia;
public:
	friend istream&operator>>(istream&is,thsinhB &s);
	friend ostream&operator<<(ostream&os,thsinhB s);
};

class thsinhA: public thisinh 
{
private:
	float toan,ly ,hoa;
public:
	friend istream&operator>>(istream&is,thsinhA &p);
	friend ostream&operator<<(ostream&os,thsinhA p);
};

#include "Bngay.h"


 istream&operator>>(istream&is,Bngay &a)
 {
   cout<<"
nhap ngay ";
   is>>a.ngay;
   cout<<"
nhap nam ";
   is>>a.thang;
   cout<<"
nhap nam ";
   is>>a.nam;
   return is;
 
 }
 ostream&operator<<(ostream&os,Bngay a)
 {
  os<<"
"<<a.ngay<<"/"<<a.thang<<"/"<<a.nam;
  return os;
 
 }
#include "Bngay.h"


 istream&operator>>(istream&is,Bngay &a)
 {
   cout<<"
nhap ngay ";
   is>>a.ngay;
   cout<<"
nhap nam ";
   is>>a.thang;
   cout<<"
nhap nam ";
   is>>a.nam;
   return is;
 
 }
 ostream&operator<<(ostream&os,Bngay a)
 {
  os<<"
"<<a.ngay<<"/"<<a.thang<<"/"<<a.nam;
  return os;
 
 }
#include "thsinhA.h"


istream&operator>>(istream&is,thsinhA &p)
{
	thisinh*tam=static_cast<thisinh*>(&p);
	is>>*tam;
	cout<<"
 nhap diem toan: ";
	is>>p.toan;
	cout<<"
 nhap diem ly";
	is>>p.ly;
	cout<<"
nhap diem hoa:";
	is>>p.hoa;
	p.tongdiem=p.toan+p.ly+p.hoa;
	return is;


}
	
ostream&operator<<(ostream&os,thsinhA p)
{
	thisinh tam=static_cast<thisinh>(p);
	os<<tam;
	os<<"
diemtoan: "<<p.toan<<"
diem ly: "<<p.ly<<"
diem hoa: "<<p.hoa;


	return os;

}
#include "thsinhB.h"

istream&operator>>(istream&is,thsinhB &p)
{
	thisinh*tam=static_cast<thisinh*>(&p);
	is>>*tam;
	cout<<"
 nhap diem toan: ";
	is>>p.van;
	cout<<"
 nhap diem ly";
	is>>p.su;
	cout<<"
nhap diem hoa:";
	is>>p.dia;
	p.tongdiem=p.van+p.su+p.dia;
	return is;


}
	
ostream&operator<<(ostream&os,thsinhB p)
{
	thisinh tam=static_cast<thisinh>(p);
	os<<tam;
	os<<"
diemvan: "<<p.van<<"
diem su: "<<p.su<<"
diem dia: "<<p.dia;


	return os;

}

và main

#include "Bngay.h"
#include "thisinh.h"
#include "thsinhA.h"
#include "thsinB.h"
#include "vector"
using namespace std;


void main()
{
	int n1,n2,tuychon,i,j;
	thsinhA tsa;
	thsinhB tsc;
	vector <thsinhA> v1;
	vector <thsinhB> v2;
	do
	{
		cout<<"
--------MENU--------";
		cout<<"
 1.NHAP THI SINH KHOI A";
		cout<<"
 2.NHAP THI SINH KHOI B";
		cout<<"
 0. THOAT CHUONG TRINH";
		do
		{
			cout<<"
 NHAP TUY CHON 0,1,2";
			cin>>tuychon;
			if (tuychon<0 || tuychon>2)
				cout<<"
 Nhap Tuy chon sai nhap lai nha......";
		}
		while( tuychon<0 || tuychon>2);
				if (tuychon == 1 )
			{
				cout <<" Nhap so thi sinh khoi A:";
				cout<<n1;
				for (i=0;i<n1;i++)
				{
					cin>>tsa;
					v1.push_back(tsa);
				}
			}
			if (tuychon == 2)
			{
				cout<<"Nhap so thi sinh khoi B 
:";
				cin>>n2;
				for(j=0;j<n2;j++)
				{
					cin>>tsc;
					v2.push_back(tsc);
				}
			}
		}
		while(tuychon!=0);

			if(n1>0)
			{
				cout<<"
 DANH SACH THI SINH THI KHOI A:";
				for(i=0;i<v1.size();i++)
					cout<<v1[i];
			}
			if(n2>0)
			{
				cout<<"
 DANH SACH THI SINH THI KHOI B:";
				for(i=0;i<v2.size();i++)
					cout<<v2[i];
			}
		system("PAUSE");
}