Удаление всех отрицательных в односвязном списке - C++

#include <iostream>
#include <windows.h>
#include <locale>
 using namespace std;

 class Node
{ 
	public:
	int numer;
	Node* next;
};
 void main()
{
	setlocale(LC_ALL,"rus");
	Node* head = NULL;
	Node* body = NULL;
	short action = -1;
	while (1)
	{
		cout<<"1. Добавить элемент"<<endl;
		cout<<"2. Просмотр списка"<<endl;
		cout<<"3. Поиск отрицательных элементов"<<endl;
		cout<<"4. Удаление первого отрицательного элемента"<<endl;
		cout<<"0. Выход"<<endl;
		cout<<"Ваш Выбор: ";
		cin>>action;

		if (action == 0)
		{
			system("CLS");
			break;
		}	
		if (action == 1)
		{
			Node* ptr = new Node;
			int m;
			cout<<"Введите Число: ";
			cin>>m;
			ptr->numer = m;
			ptr->next = NULL;
			if (head == 0)
			{	
				head = ptr;
				body = ptr;
				system("CLS");
				continue;
			}	
			body->next = ptr;
			body = ptr;
			system("CLS");
			continue;
		}

		if (action == 2)
		{
			Node* ptr = NULL;
			if (head == NULL)
			{	
				cout<<"СПИСОК ПУСТ"<<endl;
				system("PAUSE");
				system("CLS");
				continue;
			}	
			cout<<" СПИСОК "<<endl;
			ptr = head;
			while (1)
			{
				cout<<ptr->numer<<" ";
				if (ptr->next == NULL)
					break;
				ptr = ptr->next;
			}
			cout<<"\n\n";
			system("PAUSE");
			system("CLS");
			continue;
		}
		if (action == 3)
		{
			body=head;
			while (body!=NULL)
			{ 
				if (body->numer<0)
					cout<<body->numer<<" ";
				body = body->next;
			}	
			cout<<endl;
			system("PAUSE");
			system("CLS");
		}
	if (action == 4)
{
	system("CLS");
	Node* del = NULL;
	Node* last = head;

	body=head;
	while (body!=NULL)
	{
		if (body->numer<0)
		{
			
			del=body;
			body=body->next;
			last->next=body;
			if (del==head) 
				head=body;
			delete del;
		}
		else
			if(body && (body->numer<0 && body->next==NULL))
		{
			head==NULL;
		}
			else
		{
			last=body;
			body=body->next;
		}
	}
}

	cout<<endl;
	}
	}