#include <bits/stdc++.h>
using namespace std;

struct iofast_t {
    iofast_t() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} iofast;

struct uns_t {} uns;
template <typename Element, typename Head, typename ...Args>
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 <typename Element, typename Head, typename ...Args>
auto vec(uns_t, Head arg, Args ...args) {
    return vec(Element(), arg, args...);
}

template <typename Container>
auto distance(const Container &c, decltype(begin(c)) iter) {
    return distance(begin(c), iter);
}

template <typename RIter, typename Compare = less<typename iterator_traits<RIter>::value_type>>
auto isort(RIter first, RIter last, Compare comp = Compare()) {
    vector<int> 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, template <typename> typename, typename = void_t<>>
struct detect : false_type {};
template <typename T, template <typename> typename Check>
struct detect<T, Check, void_t<Check<T>>> : true_type {};
template <typename T, template <typename> typename Check>
constexpr inline bool detect_v = detect<T, Check>::value;

template <typename T>
using has_member_sort = decltype(declval<T>().sort());

template <typename Container, typename Compare = less<typename Container::value_type>>
auto sorted(Container c, Compare comp = Compare()) {
    if constexpr (detect_v<Container, has_member_sort>) {
        c.sort(comp);
        return c;
    }
    else {
        sort(begin(c), end(c), comp);
        return c;
    }
}

template <typename Container, typename Compare = equal_to<typename Container::value_type>>
auto uniqued(Container c, Compare comp = Compare()) {
    c.erase(unique(begin(c), end(c), comp), end(c));
    return c;
}

template <typename T, typename Compare = less<T>>
T &chmin(T &l, T r, Compare &&f = less<T>()) { return l = min(l, r, f); }
template <typename T, typename Compare = less<T>>
T &chmax(T &l, T r, Compare &&f = less<T>()) { return l = max(l, r, f); }

template <typename F>
constexpr auto fix(F &&f) noexcept {
    return [f = std::tuple<F>(std::forward<F>(f))](auto &&...args) mutable {
        return std::get<0>(f)(fix(std::get<0>(f)), std::forward<decltype(args)>(args)...);
    };
}

int main() {
    int n, m; cin >> n >> m;
    auto s = vec<string>(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<node *>(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;
}