#include <string>
#include <vector>
#include <list>
#include <algorithm>
#include <map>
#include <set>
#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;


class TheBrickTowerMediumDivTwo {
  public:
    vector <int> find(vector <int> heights);
    vector <int> H;
    vector <int> I;
    void Permute(int index);
};

void TheBrickTowerMediumDivTwo::Permute(int index) 
{
  int i, tmp;

  if (index == I.size()) {
    for (i = 0; i < index; i++) cout << I[i] << " ";
    cout << endl;
    return;
  }
  
  /* This is the standard recursive permutation -- swap each element in I 
     with the one in index, and call recursively on index+1 */

  for (i = index; i < I.size(); i++) {
    tmp = I[i];
    I[i] = I[index];
    I[index] = tmp;
    Permute(index+1);
    tmp = I[i];
    I[i] = I[index];
    I[index] = tmp;
  }
}

vector <int> TheBrickTowerMediumDivTwo::find(vector <int> heights)
{
  vector <int> rv;
  int i;

  H = heights;
  for (i = 0; i < H.size(); i++) I.push_back(i);
  Permute(0);
  
  return rv;
}