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

void init(void);
void add(int);
int pop(void);
void cleanup(void);
void error(void);

struct queue{
  int a;
  struct queue * next;
};

struct queue * last = 0;
struct queue * now = 0;
int count = 0;

void init(){
  if((now = malloc(sizeof(struct queue))) == NULL) error();
  last = now;
}

void add(int x){
  if(now == 0) error();
  if((now->next = malloc(sizeof(struct queue))) == NULL) error();
  now->a = x;
  now = now->next;
  count++;
}

int pop(){
  if((now == 0) || (count == 0)) error();
  int temp;
  extern int count;

  struct queue * past = last;
  temp = last->a;
  last = last->next;
  count--;
  free(past);
  return temp;
}

void cleanup(){
  if(count == 0){
  last = 0;
  now = 0;
}
  else{
    struct queue * past = last;
    while(count != 1){
      last = last->next;
      free(past);
    }
    free(last);
  }
}

void error(){
  fputs("ERROR", stderr);
  cleanup();
  exit(EXIT_FAILURE);
}