#include <iostream>
#include <fstream>

typedef unsigned int uint;


inline uint bit_count(uint i) {
  i = (i & 0x55555555) + ((i >> 1) & 0x55555555);
  i = (i & 0x33333333) + ((i >> 2) & 0x33333333);
  i = (i & 0x0f0f0f0f) + ((i >> 4) & 0x0f0f0f0f);
  i = (i & 0x00ff00ff) + ((i >> 8) & 0x00ff00ff);
  i = (i & 0x0000ffff) + ((i >> 16)& 0x0000ffff);
  return i;
}



int main() {
  std::ifstream fin("jurassic.in");

  int n;
  while(fin >> n && n != 0) {
    uint bits[24];
    for(int i = 0; i < n; i++) {
      std::string s;
      fin >> s;
      bits[i] = 0;
      for(int j = 0; j < (int)s.size(); j++) {
	bits[i] |= 1 << (s[j] - 'A');
      }
    }

    int result = 0;
    int result_bits = 0;

    uint bits_acc[24+1];
    bits_acc[0] = 0;
    for(int i = 0; i < 24; i++) {
      bits_acc[i+1] = bits_acc[i] ^ bits[i];
    }

    uint c_bits = 0;
    for(int p = 1; p < (1 << n); p++) {
      int diff = bit_count(p ^ (p - 1));
      c_bits ^= bits_acc[diff];
      if (c_bits == 0) {
	int m = bit_count(p);
	if (m > result_bits) {
	  result = p;
	  result_bits = m;
	}
      }
      //std::cout << diff << ' ' << bits_acc[diff] << std::endl;
    }

    bool first = true;
    std::cout << result_bits << std::endl;
    for(int i = 0; i < n; i++) {
      if ((result & (1 << i)) != 0) {
	if (!first)
	  std::cout << ' ';
	std::cout << (i+1);
	first = false;
      }
    }
    std::cout << std::endl;

  }
  return 0;
}