#include <cstdio>

#include <cstring>

#include <cstdlib>

#include <map>

using namespace std;

const int MAXN = ;

int N;

int A[MAXN];

char str[];

map<int , int> table;

int bitcount( int x )

{

    int res = ;

    while ( x )

    {

        if ( x &  ) ++res;

        x >>= ;

    }

    return res;

}

int main()

{

    while ( scanf( "%d", &N ) ==  )

    {

        for ( int i = ; i < N; ++i )

        {

            scanf( "%s", str );

            A[i] = ;

            for ( int j = ; str[j]; ++j )

                A[i] |= (  << ( str[j] - 'A' ) );

        }

        table.clear();

        int n1 = N / , n2 = N - n1;

        for ( int i = ; i < (  << n1 ); ++i )

        {

            int tmp = ;

            for ( int j = ; j < n1; ++j )

            if ( i & (  << j ) )

                tmp ^= A[j];

            if ( !table.count(tmp) || bitcount(i) > bitcount( table[tmp] ) ) table[tmp] = i;

        }

        int ans = ;

        for ( int i = ; i < (  << n2 ); ++i )

        {

            int tmp = ;

            for ( int j = ; j < n2; ++j )

            if ( i & (  << j ) ) tmp ^= A[ n1 + j ];

            if ( table.count(tmp) && bitcount(ans) < bitcount(i) + bitcount(table[tmp]) )

                ans = ( i << n1 ) | table[tmp];

        }

        printf("%d\n", bitcount(ans) );

        bool first = false;

        for ( int i = ; i < N; ++i )

        if ( ans & (  << i ) )

        {

            if ( first ) putchar(' ');

            printf("%d", i + );

            first = true;

        }

        puts("");

    }

    return ;

}