#include <stdio.h>
#include <stdlib.h>

typedef struct p {
    int data;
    struct p *next;
    struct p *prev;
} list;

list* init(int a);
list* insert_before(list* pc, int num);
list* start(list* pc);
list* end(list* pc);
void print(list* pc);

int main() {
    list *s, *e;
    int a, n;
    printf("Input root value of list: ");
    scanf(" %d", &a);
    list *head = init(a);
    printf("Input quantity values to insert them before root: ");
    scanf(" %d", &n);
    int *values = (int*)malloc(n * sizeof(int));
    for (int i = 0; i < n; i++) {
        scanf(" %d", &values[i]);
        insert_before(head, values[i]);
    }
    s = start(head);
    e = end(head);
    print(head);
    printf("nnStart address of list: %pnEnd address of list: %pnnstart %dnend %d", s, e, *s, *e);
    return 0;
}

list* init(int a) {
    list* root;
    root = (list*)malloc(sizeof(list));
    root->data = a;
    root->next = NULL;
    root->prev = NULL;
    return root;
}

list* insert_before(list* pc, int num) {
    list* res, *p;
    res = (list*)malloc(sizeof(list));
    p = pc->prev;
    pc->prev = res;
    res->data = num;
    res->prev = p;
    res->next = pc;
    if (p != NULL) p->next = res;
    return res;
}

list* start(list* pc) {
    while (pc->prev != NULL) {
        pc = pc->prev;
    }
    return pc;
}

list* end(list* pc) {
    while (pc->next != NULL) {
        pc = pc->next;
    }
    return pc;
}

void print(list* pc) {
    int i = 0;
    list* p;
    p = pc;
    do {
        printf("%dn", p->data);
        p = p->prev;
    } while (p != NULL);
    return;
}