#include <iostream>
#include <string>

using namespace std;

int bones[24];
int N;

int n_best_bones;
bool best_bones[24];

void recursive(int unused_joints, int depth, bool used_bones[24], int n_used_bones)
{
  if (unused_joints == 0 && n_best_bones < n_used_bones) {
    n_best_bones = n_used_bones;
    for (int i = 0; i < 24; i++) { best_bones[i] = used_bones[i]; }
  }

  if (depth >= N || n_used_bones + (N - depth) <= n_best_bones) { return; }

  used_bones[depth] = true;
  recursive(unused_joints ^ bones[depth], depth + 1, used_bones, n_used_bones + 1);
  used_bones[depth] = false;
  recursive(unused_joints               , depth + 1, used_bones, n_used_bones);
}

int main()
{

  while (cin >> N && N > 0) {
    string s; getline(cin, s);
    for (int i = 0; i < N; i++) {
      getline(cin, s);
      bones[i] = 0;
      for (int j = 0; j < s.length(); j++) {
        bones[i] |= 1 << (int)(s[j] - 'A');
      }
    }

    bool used_bones[24];
    for (int i = 0; i < 24; i++) {
      best_bones[i] = used_bones[i] = false;
    } n_best_bones = 0;
    recursive(0, 0, used_bones, 0);
    cout << n_best_bones << endl;

    bool first = true;
    for (int i = 0; i < N; i++) {
      if (best_bones[i]) {
        if (first) { first = false; }
        else { cout << " "; }
        cout << (i + 1);
      }
    } cout << endl;
  }
  return 0;
}