// >>> TEMPLATES
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using i32 = int32_t;
using i64 = int64_t;
using u32 = uint32_t;
using u64 = uint64_t;
#define int ll
using pii = pair<int, int>;
#define rep(i, n) if (const int _rep_n = n; true) for (int i = 0; i < _rep_n; i++)
#define rep1(i, n) if (const int _rep_n = n; true) for (int i = 1; i <= _rep_n; i++)
#define repR(i, n) for (int i = (int)(n)-1; i >= 0; i--)
#define rep1R(i, n) for (int i = (int)(n); i >= 1; i--)
#define loop(i, a, B) for (int i = a; i B; i++)
#define loopR(i, a, B) for (int i = a; i B; i--)
#define all(x) begin(x), end(x)
#define allR(x) rbegin(x), rend(x)
#define pb push_back
#define eb emplace_back
#define fst first
#define snd second
template <class Int> auto constexpr inf_ = numeric_limits<Int>::max()/2-1;
auto constexpr INF32 = inf_<int32_t>;
auto constexpr INF64 = inf_<int64_t>;
auto constexpr INF   = inf_<int>;
#ifdef LOCAL
#include "debug.hpp"
#define oj_local(x, y) (y)
#else
#define dump(...) (void)(0)
#define debug if (0)
#define oj_local(x, y) (x)
#endif

template <class T, class Comp> struct pque : priority_queue<T, vector<T>, Comp> {
    vector<T> &data() { return this->c; }
    void clear() { this->c.clear(); }
};
template <class T> using pque_max = pque<T, less<T>>;
template <class T> using pque_min = pque<T, greater<T>>;

template <class T, class = typename T::iterator, enable_if_t<!is_same<T, string>::value, int> = 0>
ostream& operator<<(ostream& os, T const& a) {
    bool f = true;
    for (auto const& x : a) os << (f ? "" : " ") << x, f = false;
    return os;
}
template <class T, size_t N, enable_if_t<!is_same<T, char>::value, int> = 0>
ostream& operator<<(ostream& os, const T (&a)[N]) {
    bool f = true;
    for (auto const& x : a) os << (f ? "" : " ") << x, f = false;
    return os;
}
template <class T, class = decltype(begin(declval<T&>())), class = typename enable_if<!is_same<T, string>::value>::type>
istream& operator>>(istream& is, T &a) { for (auto& x : a) is >> x; return is; }
template <class T, class S> ostream& operator<<(ostream& os, pair<T, S> const& p) {
    return os << p.first << " " << p.second;
}
template <class T, class S> istream& operator>>(istream& is, pair<T, S>& p) {
    return is >> p.first >> p.second;
}
template <class... T> ostream& operator<<(ostream& os, tuple<T...> const& t) {
    bool f = true;
    apply([&](auto&&... x) { ((os << (f ? f = false, "" : " ") << x), ...); }, t);
    return os;
}
template <class... T> istream& operator>>(istream& is, tuple<T...>& t) {
    apply([&](auto&&... x) { ((is >> x), ...); }, t);
    return is;
}
struct IOSetup {
    IOSetup() {
        cin.tie(nullptr);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(15);
    }
} iosetup;

template <class F> struct FixPoint : private F {
    constexpr FixPoint(F&& f) : F(forward<F>(f)) {}
    template <class... T> constexpr auto operator()(T&&... x) const {
        return F::operator()(*this, forward<T>(x)...);
    }
};
struct MakeFixPoint {
    template <class F> constexpr auto operator|(F&& f) const {
        return FixPoint<F>(forward<F>(f));
    }
};
#define def(name, ...) auto name = MakeFixPoint() | [&](auto &&name, __VA_ARGS__)

template <class F> struct FixPoint_d : private F {
    const char* const name;
    constexpr FixPoint_d(F&& f, const char* name) : F(forward<F>(f)), name(name) {}
    template <class... T> constexpr auto operator()(T&&... x) const {
        auto ret = F::operator()(*this, forward<T>(x)...);
#ifdef LOCAL
        cerr << name << to_s(tuple(x...)) << " -> " << to_s(ret) << '\n';
#endif
        return ret;
    }
};
struct MakeFixPoint_d {
    const char* const name;
    MakeFixPoint_d(const char* name) : name(name) {}
    template <class F> constexpr auto operator|(F&& f) const {
        return FixPoint_d<F>(forward<F>(f), name);
    }
};
#ifdef LOCAL
#define def_d(name, ...) auto name = MakeFixPoint_d(#name) | [&](auto &&name, __VA_ARGS__)
#else
#define def_d def
#endif

template <class T, size_t d> struct vec_impl {
    using type = vector<typename vec_impl<T, d-1>::type>;
    template <class... U> static type make_v(size_t n, U&&... x) {
        return type(n, vec_impl<T, d-1>::make_v(forward<U>(x)...));
    }
};
template <class T> struct vec_impl<T, 0> {
    using type = T;
    static type make_v(T const& x = {}) { return x; }
};
template <class T, size_t d = 1> using vec = typename vec_impl<T, d>::type;
template <class T, size_t d = 1, class... Args> auto make_v(Args&&... args) {
    return vec_impl<T, d>::make_v(forward<Args>(args)...);
}
template <class T> void quit(T const& x) { cout << x << '\n'; exit(0); }
template <class T, class U> constexpr bool chmin(T& x, U const& y) {
    return x > (T)y ? x = (T)y, true : false;
}
template <class T, class U> constexpr bool chmax(T& x, U const& y) {
    return x < (T)y ? x = (T)y, true : false;
}
template <class It> constexpr auto sumof(It b, It e) {
    return accumulate(b, e, typename iterator_traits<It>::value_type{});
}
template <class T, class = decltype(begin(declval<T&>()))>
constexpr auto min(T const& a) { return *min_element(begin(a), end(a)); }
template <class T, class = decltype(begin(declval<T&>()))>
constexpr auto max(T const& a) { return *max_element(begin(a), end(a)); }
template <class T> constexpr T min(set<T> const& st) { assert(st.size()); return *st.begin(); }
template <class T> constexpr T max(set<T> const& st) { assert(st.size()); return *prev(st.end()); }
template <class T> constexpr T min(multiset<T> const& st) { assert(st.size()); return *st.begin(); }
template <class T> constexpr T max(multiset<T> const& st) { assert(st.size()); return *prev(st.end()); }
constexpr ll max(signed x, ll y) { return max<ll>(x, y); }
constexpr ll max(ll x, signed y) { return max<ll>(x, y); }
constexpr ll min(signed x, ll y) { return min<ll>(x, y); }
constexpr ll min(ll x, signed y) { return min<ll>(x, y); }
template <class T> int sz(T const& x) { return x.size(); }
template <class C, class T>
int lbd(C const& v, T const& x) { return lower_bound(begin(v), end(v), x) - begin(v); }
template <class C, class T>
int ubd(C const& v, T const& x) { return upper_bound(begin(v), end(v), x) - begin(v); }
constexpr ll mod(ll x, ll m) { assert(m > 0); return (x %= m) < 0 ? x+m : x; }
constexpr ll div_floor(ll x, ll y) { assert(y != 0); return x/y - ((x^y) < 0 and x%y); }
constexpr ll div_ceil(ll x, ll y) { assert(y != 0); return x/y + ((x^y) > 0 and x%y); }
constexpr int dx[] = { 1, 0, -1, 0, 1, -1, -1, 1 };
constexpr int dy[] = { 0, 1, 0, -1, 1, 1, -1, -1 };
template <class Comp> vector<int> iota(int n, Comp comp) {
    vector<int> idx(n);
    iota(begin(idx), end(idx), 0);
    stable_sort(begin(idx), end(idx), comp);
    return idx;
}
constexpr int popcnt(ll x) { return __builtin_popcountll(x); }
mt19937_64 seed_{random_device{}()};
template <class Int> Int rand(Int a, Int b) { return uniform_int_distribution<Int>(a, b)(seed_); }
i64 irand(i64 a, i64 b) { return rand<i64>(a, b); } // [a, b]
u64 urand(u64 a, u64 b) { return rand<u64>(a, b); } //
template <class It> void shuffle(It l, It r) { shuffle(l, r, seed_); }
template <class V> V &operator--(V &v) { for (auto &x : v) --x; return v; }
template <class V> V &operator++(V &v) { for (auto &x : v) ++x; return v; }
bool next_product(vector<int> &v, int m) {
    repR (i, v.size()) if (++v[i] < m) return true; else v[i] = 0;
    return false;
}
bool next_product(vector<int> &v, vector<int> const& s) {
    repR (i, v.size()) if (++v[i] < s[i]) return true; else v[i] = 0;
    return false;
}
template <class Vec> int sort_unique(Vec &v) {
    sort(begin(v), end(v));
    v.erase(unique(begin(v), end(v)), end(v));
    return v.size();
}
template <class Vec, class Comp> int sort_unique(Vec &v, Comp comp) {
    sort(begin(v), end(v), comp);
    v.erase(unique(begin(v), end(v)), end(v));
    return v.size();
}
template <class It> auto prefix_sum(It l, It r) {
    vector<typename It::value_type> s = { 0 };
    while (l != r) s.emplace_back(s.back() + *l++);
    return s;
}
template <class It> auto suffix_sum(It l, It r) {
    vector<typename It::value_type> s = { 0 };
    while (l != r) s.emplace_back(*--r + s.back());
    reverse(s.begin(), s.end());
    return s;
}
template <class T> T pop(vector<T> &a) { auto x = a.back(); a.pop_back(); return x; }
template <class T> T pop_back(vector<T> &a) { auto x = a.back(); a.pop_back(); return x; }
template <class T, class V, class C> T pop(priority_queue<T, V, C> &a) { auto x = a.top(); a.pop(); return x; }
template <class T> T pop(queue<T> &a) { auto x = a.front(); a.pop(); return x; }
template <class T> T pop_front(deque<T> &a) { auto x = a.front(); a.pop_front(); return x; }
template <class T> T pop_back(deque<T> &a) { auto x = a.back(); a.pop_back(); return x; }
template <class T> T pop_front(set<T> &a) { auto x = *a.begin(); a.erase(a.begin()); return x; }
template <class T> T pop_back(set<T> &a) { auto it = prev(a.end()); auto x = *it; a.erase(it); return x; }
template <class T> T pop_front(multiset<T> &a) { auto it = a.begin(); auto x = *it; a.erase(it); return x; }
template <class T> T pop_back(multiset<T> &a) { auto it = prev(a.end()); auto x = *it; a.erase(it); return x; }
template <class A, class B>
pair<vector<A>, vector<B>> unzip(vector<pair<A, B>> const& c) {
    vector<A> a;
    vector<B> b;
    for (auto const& [x, y] : c) {
        a.push_back(x);
        b.push_back(y);
    }
    return { a, b };
}
template <class A, class B>
pair<vector<A>, vector<B>> unzip(map<A, B> const& c) {
    vector<A> a;
    vector<B> b;
    for (auto const& [x, y] : c) {
        a.push_back(x);
        b.push_back(y);
    }
    return { a, b };
}
// <<<
// >>> min cost b-flow
// https://misawa.github.io/others/flow/lets_use_capacity_scaling.html
template <class Flow, class Cost> struct MinCostFlow { // capacity scaling
    struct Edge {
        int32_t from, to, rev;
        Flow cap, flow;
        Cost cost;
        Edge(int from, int to, int rev, Flow cap, Cost cost)
            : from(from), to(to), rev(rev), cap(cap), flow(0), cost(cost) {}
    };
    vector<vector<Edge>> g;
    vector<pair<int32_t, int32_t>> es;
    vector<Flow> b;
    vector<Cost> p, dist;
    vector<int32_t> pv, pe, S, T;
    int V, E = 0;
    Cost max_dist;

    MinCostFlow(int V = 0) : g(V), b(V), p(V), pv(V, -1), pe(V, -1), V(V) {}
    int add_edge(int from, int to, Flow lower_cap, Flow upper_cap, Cost cost) {
        assert(0 <= from and from < V);
        assert(0 <= to and to < V);
        assert(lower_cap <= upper_cap);
        es.emplace_back(from, g[from].size());
        g[from].emplace_back(from, to, g[to].size() + (from == to ? 1 : 0), upper_cap, cost);
        g[to].emplace_back(to, from, g[from].size()-1, -lower_cap, -cost);
        return E++;
    }
    Edge edge(int id) const {
        assert(0 <= id); assert(id < (int)es.size());
        auto [from, idx] = es[id];
        return g[from][idx];
    }

    template <class T> static constexpr bool chmin(T &x, T const& y) {
        return x > y ? (x = y, true) : false;
    };
    void push(Edge &e, Flow f) {
        e.flow += f;
        g[e.to][e.rev].flow -= f;
        b[e.from] -= f;
        b[e.to] += f;
    }
    Flow rcap(Edge const& e) const { return e.cap - e.flow; }
    Cost rcost(Edge const& e) const { return e.cost + p[e.from] - p[e.to]; }

    pair<Cost, bool> run() {
        p.resize(V);
        for (auto &es : g) for (auto &e : es) if (rcap(e) < 0) push(e, rcap(e));

        Flow inf_flow = 1;
        for (auto &es : g) for (auto &e : es) inf_flow = max(inf_flow, rcap(e));
        Flow delta = 1;
        while (delta <= inf_flow) delta <<= 1;
        for (delta >>= 1; delta; delta >>= 1) {
            S.clear();
            T.clear();
            for (auto &es : g) {
                for (auto &e : es) {
                    if (rcost(e) < 0 and rcap(e) >= delta) {
                        push(e, rcap(e));
                    }
                }
            }
            for (int32_t x = 0; x < V; x++) {
                if (b[x] >= +delta) S.push_back(x);
                if (b[x] <= -delta) T.push_back(x);
            }
            while (dual(delta)) primal(delta);
        }
        Cost ans = 0;
        for (auto [from, idx] : es) {
            auto const& e = g[from][idx];
            ans += e.flow * e.cost;
        }
        return { ans, S.empty() and T.empty() };
    }
    bool dual(Flow delta) {
        using P = pair<Cost, int32_t>;
        static auto comp = [](P const& p, P const& q) { return p.first > q.first; };
        using PQ = priority_queue<P, vector<P>, decltype(comp)>;
        struct pque : PQ {
            pque() : PQ(comp) {}
            void clear() { this->c.clear(); }
        };
        static pque pq;

        static auto const inf_cost = max<Cost>(numeric_limits<Cost>::max(),
                                               numeric_limits<uint64_t>::max());
        dist.assign(V, inf_cost);
        pv.assign(V, -1);
        pe.assign(V, -1);
        S.erase(remove_if(begin(S), end(S),
                          [&](int x) { return b[x] < +delta; }), end(S));
        T.erase(remove_if(begin(T), end(T),
                          [&](int x) { return b[x] > -delta; }), end(T));
        if (T.empty()) return false;
        pq.clear();
        for (int s : S) pq.emplace(dist[s] = 0, s);

        max_dist = 0;
        size_t cnt = 0;
        while (pq.size()) {
            auto [d, x] = pq.top(); pq.pop();
            if (dist[x] < d) continue;
            max_dist = d;
            if (b[x] <= -delta and ++cnt >= T.size()) break;
            for (size_t i = 0; i < g[x].size(); i++) {
                auto const& e = g[x][i];
                if (rcap(e) >= delta and chmin(dist[e.to], d + rcost(e))) {
                    pv[e.to] = x, pe[e.to] = i;
                    pq.emplace(dist[e.to], e.to);
                }
            }
        }
        for (int x = 0; x < V; x++) p[x] += min(dist[x], max_dist);
        return cnt > 0;
    }
    void primal(Flow delta) {
        for (int t : T) {
            if (dist[t] > max_dist) continue;
            Flow f = -b[t];
            int x;
            for (x = t; pv[x] >= 0 and f >= delta; x = pv[x]) {
                chmin(f, rcap(g[pv[x]][pe[x]]));
            }
            chmin(f, b[x]);
            if (f < delta) continue;
            x = t;
            while (true) {
                auto &y = pv[x];
                if (y < 0) break;
                push(g[y][pe[x]], f);
                x = y, y = -1;
            }
        }
    }
    // tuple<Flow, Cost, bool> max_flow(int s, int t) {
    //     assert(s != t);

    //     Flow inf_flow = abs(b[s]);
    //     for (auto const& e : g[s]) inf_flow += max<Flow>(e.cap, 0);
    //     add_edge(t, s, 0, inf_flow, 0);
    //     auto pop = [&]() {
    //         g[s].pop_back();
    //         g[t].pop_back();
    //         es.pop_back();
    //     };
    //     auto [cost, ok] = run();
    //     if (not ok) {
    //         pop();
    //         return { 0, cost, false };
    //     }

    //     inf_flow = abs(b[s]);
    //     for (auto const& e : g[s]) inf_flow += rcap(e);
    //     b[s] += inf_flow, b[t] -= inf_flow;
    //     tie(cost, ok) = run();
    //     b[s] -= inf_flow, b[t] += inf_flow;
    //     pop();
    //     return { b[t], cost, true };
    // }
#ifdef LOCAL
    friend string to_s(MinCostFlow a) {
        string ret = "\n";
        ret += "V = " + to_s(a.V) + ", E = " + to_s(a.E) + "\n";
        for (int id = 0; id < a.E; id++) {
            auto [from, idx] = a.es[id];
            auto const& e = a.g[from][idx];
            auto const& r = a.g[e.to][e.rev];
            ret += to_s(id) + " : ";
            ret += to_s(e.from) + "->" + to_s(e.to) + ", ";
            ret += "flow " + to_s(e.flow) + " in [" + to_s(-r.cap) + ", " + to_s(e.cap) + "], ";
            ret += "cost " + to_s(e.cost) + "\n";
        }
        return ret;
    }
#endif
};
// <<<

int32_t main() {
    int n, m; cin >> n >> m;
    auto adj = make_v<int, 2>(n, n);
    rep (i, m) {
        int a, b; cin >> a >> b; --a, --b;
        adj[a][b] = adj[b][a] = 1;
    }

    MinCostFlow<int, int> g(2*n);
    rep (i, n) rep (j, n) {
        if (i == j) continue;
        g.add_edge(i, n+j, 0, 1, 1-adj[i][j]);
    }
    rep (i, n) {
        g.b[i] = 1;
        g.b[n+i] = -1;
    }

    auto [cost, ok] = g.run();
    assert(ok);
    dump(cost);

    cout << n-cost*2 << '\n';

}