#include <iostream>
#include <fstream>
#include <string>

#define N (24)

using namespace std;

int main(void)
{
	ifstream cin("jurassic.in");

	int n;

	while(cin >> n, n) {
		static int mask[N];
		string s;

		for(int i = 0; i < n; i++) {
			mask[i] = 0;
			cin >> s;
			for(int j = 0; j < s.length(); j++)
				mask[i] |= 1 << (s[j] - 'A');
		}

		int mk = 0;
		int mi = 0;

		for(int i = 0; i < (1 << n); i++) {
			int j = 0;
			int k = 0;
			int s = 0;

			for(int ii = i, j = 0; ii > 0; ii >>= 1, j++) {
				if((ii & 1) == 1) {
					s ^= mask[j]; k++;
				}
			}

			if(s == 0 && mk < k) { mk = k; mi = i; }
		}

		cout << mk << endl;

		{
			for(int ii = mi, j = 0; ii > 0; ii >>= 1, j++) {
				if((ii & 1) == 1) {
					cout << j + 1;
					if(ii > 1) cout << " ";
				}
			}
		}

		cout << endl;
	}

	return 0;
}