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

typedef struct data
{
    int a;
    struct data *next;
    struct data *pre;
}data;

data *head=NULL;
data *tail=NULL;

int deQueue ()
{

    int x;
    data *temp=head;

    if(head==NULL){
        printf("nothing\n");
        return -1;
    }

    else if(temp->next==NULL){
        head=NULL;
        tail=NULL;
        free(temp);
        return x;
    }
    head=temp->next;
    x=temp->a;
    free(temp);
    head->pre=NULL;
    return x;

}

void enQueue (int x){
 data *newnode=(data*)malloc(sizeof(data));
 newnode->a=x;
 newnode->next=NULL;
 newnode->pre=NULL;

 if(head==NULL){
    head=newnode;
    tail=newnode;
    return ;
 }
 newnode->pre=tail;
 tail->next=newnode;
 tail=newnode;

}



void print()
{
    data *temp=head;
    while(temp!=NULL){
        printf(" %d\n",temp->a);
        temp=temp->next;
    }
    printf("\n");
}
int main ()
{
    int p;
    enQueue(4);
    enQueue(2);
    enQueue(7);
print();
    p=deQueue();
    printf("deQueue %d\n",p);

    p=deQueue();
    printf("deQueue %d\n",p);

    print();
}