#include <iostream>

using namespace std;
//UNSHIFT
void f_unshift(int array_of_elements[],int size,int& head,int tail,int new_element,bool& empty)
{
    if ((head==tail)&&(empty==true))
    {
        array_of_elements[head]=new_element;
        head++;
        empty = false;
        return;
    }
    if ((head==tail)&&(empty==false))
        return;
    array_of_elements[head]=new_element;
    if (head!=size-1)
    {
        head++;
        return;
    }
    if (head==size-1)
        head=0;
}
//SHIFT
int f_shift(int array_of_elements[],int size,int& head,int tail,bool& empty)
{
    int b;
    if ((head==tail)&&(empty==true))
        return 404;
    if (head==0)
    {
        head=size-1;
        b=array_of_elements[head];
        array_of_elements[head]=0;
        if ((head==tail)&&(empty==false))
            empty = true;
        return b;
    }
    head--;
    b=array_of_elements[head];
    array_of_elements[head]=0;
    if ((head==tail)&&(empty==false))
            empty = true;
    return b;
}
//PUSH
void f_push(int array_of_elements[],int size,int head,int& tail,int new_element,bool& empty)
{
    if ((head==tail)&&(empty==true))
    {
        empty=false;
        if (tail==0)
        {
            tail=size-1;
            array_of_elements[tail]=new_element;
            return;
        }
        tail--;
        array_of_elements[tail]=new_element;
        return;
    }
    if ((head==tail)&&(empty==false))
        return;
    if (tail==0)
    {
        tail=size-1;
        array_of_elements[tail]=new_element;
        return;
    }
    tail--;
    array_of_elements[tail]=new_element;
}
//POP
int f_pop(int array_of_elements[],int size,int head,int& tail,bool& empty)
{
    int b;
    if ((head==tail)&&(empty==true))
        return 404;
    if (tail==size-1)
    {
        tail=0;
        b=array_of_elements[size-1];
        array_of_elements[size-1]=0;
        if ((head==tail)&&(empty==false))
            empty=true;
        return b;
    }
    tail++;
    b=array_of_elements[tail-1];
    array_of_elements[tail-1]=0;
    if ((head==tail)&&(empty==false))
        empty=true;
    return b;
}
// FOR TEST
void f_clean_array(int array[],int size)
{
    for (int i=0;i<size;i++)
        array[i]=0;
}
int main()
{
    int size = 10;
    int array_of_elements[size];
    f_clean_array(array_of_elements,size);
    int head = 0;
    int tail = 0;
    bool empty = true;
    int k = 0;
    //TEST

    cout << "UNSHIFT = 1" << endl << "SHIFT = 2" << endl << "PUSH = 3" << endl << "POP = 4" << endl;
    while (k==0)
    {
        int a;
        cin >> a;
        if (a==1)
        {
            cout << "UNSHIFT : ";
            int b;
            cin >> b;
            f_unshift(array_of_elements,10,head,tail,b,empty);
        }
        if (a==2)
            cout << "SHIFT : " << f_shift(array_of_elements,size,head,tail,empty) << endl;
        if (a==3)
        {
            cout << "PUSH: ";
            int b;
            cin >> b;
            f_push(array_of_elements,size,head,tail,b,empty);
        }
        if (a==4)
            cout << "POP   : " << f_pop(array_of_elements,size,head,tail,empty) << endl;
        for (int i=0;i<size;i++)
            cout << array_of_elements[i] << " ";
        cout << endl << "HEAD : " << head << " TAIL : " << tail << endl;

    }
    //TEST END

}