Nika dlist

#include<iostream>
using namespace std;
struct dlist
{
    int info;
    dlist *prev, *next;
};



int main()
{
    int k = 0;  //проверка на случай наличия одного элемента в спике
    //объявление головы списка
    int x;
    cin >> x; k++;
    dlist *head = new dlist;
    head->info = x;
    head->prev = nullptr; head->next = nullptr;
    dlist *p = new dlist;
    p = head;

    //ввод тела списка
    cin >> x;
    while(x!=0)
    {
        k++;
        dlist *r = new dlist;
        r->info = x; r->prev=nullptr; r->next=nullptr;
        p->next = r;
        r->prev=p;
        p = r;
        cin >> x;
    }

    if(k==1){cout << "В списке недостаточное количество элементов"; return 0;}

    //проверка на убывание
    int f = 1;
    p = head->next;
    while(p!=nullptr)
    {
        if(p->info>=p->prev->info){f = 0; break;}
        p=p->next;
    }

    if(f == 1)
    {
        p = head->next;
        while(p!=nullptr)
        {
            if(p->info%5==0&&p->prev->info%5==0)
            {
                int x = p->info + p->prev->info;
                dlist *r = new dlist;
                r->info = x;
                r->prev = p->prev;
                r->next = p;
                p->prev->next = r;
                p->prev = r;
            }
            p = p->next;
        }
    }
    else {
        int a, b;
        cout << "a: ";
        cin >> a;
        cout << "b: ";
        cin >> b;
        p = head;
        while (p != nullptr) {
            if (p->next == nullptr) { break; }
            if (p->info >= a && p->info <= b) {
                dlist *r;
                if (p->next->next != nullptr) //... p y z NULL
                {
                    r = p->next;
                    p->next = p->next->next;
                    p->next->prev = p;
                    r->next = nullptr;
                    r->prev = nullptr;
                    delete r;
                    p = p->next;
                } else if (p->next != nullptr)//... p y NULL
                {
                    r = p->next;
                    p->next = nullptr;
                    r->next = nullptr;
                    r->prev = nullptr;
                    delete r;
                    p = p->next;
                } else {
                    p = p->next;
                }
            } else {
                p = p->next;
            }
        }
    }
    //вывод списка
    p = head;
    while(p!=nullptr)
    {
        cout << p->info << " ";
        p = p->next;
    }

    //удаление списка
    while(head!=nullptr)
    {
        dlist *r = head;
        head = head->next;
        delete r;
    }
}