#include<stdio.h>
#include<stdlib.h>
#define queuesize 4
int q[queuesize];
void enqueue(int item);
void dequeue();
void display();
int r=-1;
int f=0;
int main()
{
    int ch,item;
    printf("\n");
    while(1)
    {
        scanf("%d",&ch);
        switch(ch)
        {
            case 1 : scanf("%d",&item);
                     enqueue(item);break;
            case 2 : dequeue();break;
            case 3 : display();break;
            case 4 : if(r==queuesize-1)
                     {
                         printf("Queue Full\n");
                     }
                     else
                     {
                         printf("Queue not Full\n");
                     };break;
            case 5 : if(f>r)
                     {
                        printf("Queue Empty\n");
                     }
                     else
                     {
                        printf("Queue not Empty\n");
                     };break;
            case 6 : exit(0);
            default: printf("Invalid Choice\n");     
        }
    }
    return 0;
}

void enqueue(int item)
{
    if(r==queuesize-1)
    {
        printf("Queue Overflow\n");
        return;
    }
    r=r+1;
    q[r]=item;
}

void dequeue()
{
    if(f>r)
    {
        printf("Queue Underflow\n");
        return;
    }
    printf("Dequeued element is : %d\n",q[f]);
    f++;
    if(f>r)
    {
        r=-1;
        f=0;
    }
}

void display()
{
    if(f>r)
    {
        printf("Queue Empty - No elements to display\n");
        return;
    }
    printf("The elements of Queue are :");
    for(int i=f;i<=r;i++)
    {
        printf("%d ",q[i]);
    }
    printf("\n");
}