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

int *prev,*next;

int main()
{
int n;
int i,nextInList,prevInList;

scanf("%d",&n);
prev=(int*) malloc((n+1)*sizeof(int));
next=(int*) malloc((n+1)*sizeof(int));
if (!prev || !next)
{
  printf("malloc failed %d\n",__LINE__);
  exit(0);
}
for (i=0;i<n;i++)
{
  prev[i]=i-1;
  next[i]=i+1;
}
next[n]=0;
prev[n]=n-1;
prev[0]=n;
while (1)
{
  scanf("%d",&i);
  switch (i)
  {
    case 0:
      printf("Terminate\n");
      exit(0);
    case 1: // Indicate some free number
      if (next[n]==n)
        printf("No elements free!\n");
      else
        printf("%d is free\n",next[n]);
      break;
    case 2: // Change number from free to allocated
      scanf("%d",&i);
      if (i<0 || i>=n)
      {
        printf("Range error %d\n",__LINE__);
        exit(0);
      }
      if (next[i]==(-1))
      {
        printf("Already allocated\n");
        break;
      }
      nextInList=next[i];
      prevInList=prev[i];
      prev[nextInList]=prevInList;
      next[prevInList]=nextInList;
      next[i]=prev[i]=(-1);
      break;
    case 3:  // Change number from allocated to free
      scanf("%d",&i);
      if (i<0 || i>=n)
      {
        printf("Range error %d\n",__LINE__);
        exit(0);
      }
      if (next[i]!=(-1))
      {
        printf("Already free\n");
        break;
      }
      prevInList=n;
      nextInList=next[n];
      prev[i]=prevInList;
      next[i]=nextInList;
      next[prevInList]=i;
      prev[nextInList]=i;
      break;
    case 4:  // List entire free list
      printf("Free list: ");
      for (i=next[n];i!=n;i=next[i])
        printf("%d ",i);
      printf("\n");
      break;
    case 5:  // List entire free list in reverse
      printf("Free list: ");
      for (i=prev[n];i!=n;i=prev[i])
        printf("%d ",i);
      printf("\n");
      break;
    default:
      printf("No matching case %d\n",__LINE__);
      exit(0);
  }
}
}