#include <string>
#include <iostream>
using namespace std;

void fill_in(int index, int c_ok, string &s)
{
  if (index == 10) {
    if (!c_ok) cout << s << endl;
    return;
  }

  s[index] = 'A';
  fill_in(index+1, c_ok, s);

  s[index] = 'B';
  fill_in(index+1, c_ok, s);

  if (c_ok) {
    s[index] = 'C';
    fill_in(index+1, 0, s);
  }
}

main()
{
  int i, j, k;
  string s;

  s.resize(10, ' ');
  fill_in(0, 1, s);
}