#include <iostream>

class List {
private:
    struct node {
        int data;
        node* link;
    } *p;
public:
    List() { p= NULL; }
    void append(int number) {
        node* x;
        node* y;

        if(p == NULL) {
            p = new node;
            p->data = number;
            p->link = NULL;
        }
        else {
            x = p;
            while(x->link != NULL)
                x = x->link;
            y = new node;
            y->data = number;
            y->link = NULL;
            x->link = y;
        }
    }
    void addfirst(int number) {
        node* x;
        x = new node;
        x->data = number;
        x->link = p;
        p = x;
    }
    void addafter(int a, int number) {
        node* x;
        node* y;
        int i;
        for(i=0,x=p; i<a;i++) {
            x = x->link;
            if(x == NULL) {
                std::cout << "You need at least " << a << " elements.\n";
                return;
            }
        }
        y = new node;
        y->data = number;
        y->link = x->link;
        x->link = y;
    }
    void del(int number) {
        node* x;
        node* z;
        x = p;
        if (x->data == number) {
            p = x->link;
            delete x;
            return;
        }

        z = x;
        while(x!=NULL) {
            if (x->data == number) {
                z->link = x->link;
                delete x;
                return;
            }
            z = x;
            x = x->link;
        }
        std::cout << "Element " << number << " not found.";
    }
    void display() {
        node* x;
        std::cout << "\n";
        for(x = p; x != NULL; x = x->link)
            std::cout << x->data << std::endl;
    }
    int count() {
        node* x;
        int counter = 0;
        for(x=p; x != NULL; x = x->link)
            counter++;

        return counter;
    }
    ~List() {
        node* x;
        if (p == NULL)
            return;

        while( p != NULL) {
            x = p->link;
            delete p;
            p = x;
        }
    }
};