Cho e hỏi bài này bị lỗi gì ạ

#include<iostream>
#include<string>
#include<iomanip>

using namespace std;

class NhaSX{
	string TenNSX;
	char DC[30];
	friend class May;
	friend class Maytinh;
	//friend void In(Maytinh*a, int n);
	//friend void Xoa(Maytinh *a, int *n);
};

class May{
	public:
		char NH[30];
		NhaSX NSX;
		float GT;
		void nhap();
		void xuat();
		
};

class Maytinh:public May{
	float TD;
	int DLR;
	int DLHDD;
	public: 
		void nhap();
		void xuat();
		friend void In(Maytinh *a, int n);
		friend void Sap(Maytinh *a,int n);
		friend void Xoa(Maytinh *a, int *n);
};

void May::nhap(){
	cout<<"nhap nhan hieu: ";
	gets(NH);
	fflush(stdin);
	cout<<"ten nha san xuat: ";
	getline(cin,NSX.TenNSX);
	fflush(stdin);
	cout<<"Dia chi: ";
	gets(NSX.DC);
	fflush(stdin);
	cout<<"Gia thanh: ";
	cin>>GT;
}

void May::xuat(){
	cout<<"Nhan hieu: "<<NH<<endl;
	cout<<"Ten NSX: "<<NSX.TenNSX<<endl;
	cout<<"Dia chi: "<<NSX.DC<<endl;
	cout<<"Gia thanh: "<<GT<<endl;
}

void Maytinh::nhap(){
	May::nhap();
	cout<<"Toc do: ";
	cin>>TD;
	cout<<"Dung luong Ram: ";
	cin>>DLR;
	cout<<"Dung luong HDD: ";
	cin>>DLHDD;
}

void Maytinh::xuat(){
	May::xuat();
	cout<<"Toc do: "<<TD<<endl;
	cout<<"dung luong Ram: "<<DLR<<endl;
	cout<<"Dung luong HDD"<<DLHDD<<endl;
}

void In(Maytinh a[100], int n){
	for(int i=0;i<n;i++)
	if(strcmp(a[i].NSX.TenNSX,"IBM")==0)
	a[i].xuat();
}

void Sap(Maytinh a[100], int n){
	int i,j;
	Maytinh tg;
	for(i=0;i<n;i++)
		for(j=i+1;j<n;j++)
	if(a[j].GT<a[i].GT){
		tg=a[i];
		a[i]=a[j];
		a[j]=tg;
	}
}

void Xoa(Maytinh a[100], int *n){
	for(int i=0;i<*n;i++)
	while(strcmp(a[i].NSX.TenNSX,"Intel")==0)
	{
		for(int j=i;j<*n;j++)
		a[j]=a[j+1];
		*n=*n-1;
	}
	
	int main(){
		int n, i;
		Maytinh a[100];
		cout<<"nhap vao so luong may tinh: ";
		cin>>n;
		for(i=0;i<n;i++)
			a[i].nhap();
		cout<<"--May tinh cua hang IBM--"<<endl;
			In(a,n);
		cout<<"--Sap xep may tinh tang dan--"<<endl;
			Sap(a,n);
		for(i=0;i<n;i++)
			a[i].xuat();
		
		for(i=0;i<n;i++)
			a[i].xuat();
		cout<<"--Ds may tinh con lai sau khi xoa--"<<endl;
			Xoa(a,&n);
		for(i=0;i<n;i++)
			a[i].xuat();
			
		system("pause");	
		return 0;
	}
}