void lcs(seq const & xs, seq const & ys, seq & an_lcs)
{
members xs_in_lcs(xs.size(), false);
calculate_lcs(xs.begin(), xs.begin(), xs.end(),
ys.begin(), ys.end(), xs_in_lcs);
set_lcs(xs.begin(), xs_in_lcs, back_inserter(an_lcs));
}
