#include using namespace std; struct iofast_t { iofast_t() { ios::sync_with_stdio(false); cin.tie(nullptr); } } iofast; struct uns_t {} uns; template auto vec(Element init, Head arg, Args ...args) { if constexpr (sizeof...(Args) == 0) return vector(arg, init); else return vector(arg, vec(init, args...)); } template auto vec(uns_t, Head arg, Args ...args) { return vec(Element(), arg, args...); } template auto distance(const Container &c, decltype(begin(c)) iter) { return distance(begin(c), iter); } template ::value_type>> auto isort(RIter first, RIter last, Compare comp = Compare()) { vector i(distance(first, last)); iota(begin(i), end(i), 0); sort(begin(i), end(i), [&](auto x, auto y) { return comp(*(first + x), *(first + y)); }); return i; } template typename, typename = void_t<>> struct detect : false_type {}; template typename Check> struct detect>> : true_type {}; template typename Check> constexpr inline bool detect_v = detect::value; template using has_member_sort = decltype(declval().sort()); template > auto sorted(Container c, Compare comp = Compare()) { if constexpr (detect_v) { c.sort(comp); return c; } else { sort(begin(c), end(c), comp); return c; } } template > auto uniqued(Container c, Compare comp = Compare()) { c.erase(unique(begin(c), end(c), comp), end(c)); return c; } template > T &chmin(T &l, T r, Compare &&f = less()) { return l = min(l, r, f); } template > T &chmax(T &l, T r, Compare &&f = less()) { return l = max(l, r, f); } template constexpr auto fix(F &&f) noexcept { return [f = std::tuple(std::forward(f))](auto &&...args) mutable { return std::get<0>(f)(fix(std::get<0>(f)), std::forward(args)...); }; } int main() { int n, m; cin >> n >> m; auto s = vec(uns, m); for (auto &e : s) cin >> e; if (n == 1) { cout << "Yes" << endl; return 0; } struct node { node(): c{ nullptr, nullptr }, exists{ false, false }, ch(-1) { } ~node() { // ぬるぽ ok delete c[0]; delete c[1]; } node *advance(bool b) { if (c[b] == nullptr) { c[b] = new node(); } return c[b]; } node *c[2]; bool exists[2]; int ch; }; auto dep = vec(nullptr, n + 1, 0); node root; for (auto &v : s) { int d = 0; auto iter = &root; while (d < n) { auto next = iter->advance(v[d] - '0'); next->exists[0] = iter->exists[0]; next->exists[1] = iter->exists[1]; if (0 <= iter->ch) { next->exists[iter->ch] = true; } next->ch = v[d] - '0'; iter = next; ++d; dep[d].push_back(iter); } } for (int d = n; 2 <= d; --d) { bool f = false; for (auto p : dep[d]) { f |= (p->exists[!p->ch]); } if (!f) { cout << "No" << endl; return 0; } } cout << "Yes" << endl; }