enque deque avr

#include<stdio.h>
#include<stdlib.h>
typedef struct Data
{
    int a;
    struct Data *next,*prev;
}Data;
Data *head=NULL, *tail=NULL;

void enQueue(int x)
{
    Data *new_node=(Data*)malloc(sizeof(Data));
    new_node->a=x;
    new_node->next=NULL;
    new_node->prev=NULL;
    if(head==NULL)
    {
        head=new_node;
        tail=head;
        return;
    }
    new_node->prev=tail;
    tail->next=new_node;
    tail=new_node;
}

int deQueue()
{
    Data *dlt=head;
    int x;
    if(head==NULL)
    {
        printf("Empty!\n");
        return -1;
    }
    else if(head->next==NULL)
    {
        head=NULL;
        tail=NULL;
        x = dlt -> a;
        free(dlt);
        return x;
    }
    head=head->next;
    head->prev=NULL;
    x = dlt -> a;
    free(dlt);
    return x;
}

void Print()
{
    int x=0;
    Data *tmp=head;
    while(tmp!=NULL)
    {
        printf("%d. Enqueued Value: %d\n", ++x, tmp -> a);
        tmp=tmp->next;
    }
}

int main()
{
    int i,n,DQ=0;
    float ttl,avr,sum=0;
    printf("Enter number of Enqueue: ");
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
        int vlu;
        printf("\nEnter Enqueue Value %d: ",i+1);
        scanf("%d",&vlu);
        enQueue(vlu);
    }
    Print();
    int j,m;
    printf("\nEnter number of Dequeue: ");
    scanf("%d",&m);
    if(m>n)
    {
        for(j=0;j<n;j++)
    {
        int ttl;
        ttl = deQueue();
        sum+=ttl;
    }
    Print();
    avr=sum/n;
    printf("\nAverage: %.2f",avr);

        return;
    }
    for(j=0;j<m;j++)
    {
        int ttl;
        ttl = deQueue();
        sum+=ttl;
    }
    Print();
    avr=sum/m;
    printf("\nAverage: %.2f",avr);


    return 0;
}