#include "bits/stdc++.h"
#include <random>
#include <chrono>
#define ALL(x) (x).begin(), (x).end()
#define RALL(x) (x).rbegin(), (x).rend()
#define SZ(x) ((lint)(x).size())
#define FOR(i, begin, end) for(lint i=(begin),i##_end_=(end);i<i##_end_;++i)
#define IFOR(i, begin, end) for(lint i=(end)-1,i##_begin_=(begin);i>=i##_begin_;--i)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
#define endk '\n'
using namespace std; typedef unsigned long long _ulong; typedef long long int lint; typedef double ld; typedef pair<lint, lint> plint; typedef pair<ld, ld> pld;
struct fast_ios { fast_ios() { cin.tie(nullptr), ios::sync_with_stdio(false), cout << fixed << setprecision(30); }; } fast_ios_;
template<class T> auto add = [](T a, T b) -> T { return a + b; };
template<class T> auto mul = [](T a, T b) -> T { return a * b; };
template<class T> auto f_max = [](T a, T b) -> T { return max(a, b); };
template<class T> auto f_min = [](T a, T b) -> T { return min(a, b); };
template<class T> using V = vector<T>;
using Vl = V<lint>; using VVl = V<Vl>; using VVVl = V<V<Vl>>;
template< typename T > ostream& operator<<(ostream& os, const vector< T >& v) {
    for (int i = 0; i < (int)v.size(); i++) os << v[i] << (i + 1 != v.size() ? " " : "");
    return os;
}
template< typename T >istream& operator>>(istream& is, vector< T >& v) {
    for (T& in : v) is >> in;
    return is;
}
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
template <class T>
T div_floor(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a >= 0 ? a / b : (a + 1) / b - 1;
}
template <class T>
T div_ceil(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a > 0 ? (a - 1) / b + 1 : a / b;
}
template <class F> struct rec {
    F f;
    rec(F&& f_) : f(std::forward<F>(f_)) {}
    template <class... Args> auto operator()(Args &&... args) const {
        return f(*this, std::forward<Args>(args)...);
    }
};
lint gcd(lint a, lint b) { if (b == 0) return a; else return gcd(b, a % b); }
lint digit(lint a) { return (lint)log10(a); }
lint e_dist(plint a, plint b) { return abs(a.first - b.first) * abs(a.first - b.first) + abs(a.second - b.second) * abs(a.second - b.second); }
lint m_dist(plint a, plint b) { return abs(a.first - b.first) + abs(a.second - b.second); }
bool check_overflow(lint a, lint b, lint limit) { if (b == 0) return false; return a > limit / b; } // a * b > c => true
void Worshall_Floyd(VVl& g) { REP(k, SZ(g)) REP(i, SZ(g)) REP(j, SZ(g)) chmin(g[i][j], g[i][k] + g[k][j]); }
const long long MOD1000000007 = 1000000007, MOD998244353 = 998244353, INF = 1e18;
lint dx[8] = { 0, 1, 0, -1, 1, -1, 1, -1 }, dy[8] = { 1, 0, -1, 0, -1, -1, 1, 1 };
bool YN(bool flag) { cout << (flag ? "YES" : "NO") << endk; return flag; } bool yn(bool flag) { cout << (flag ? "Yes" : "No") << endk; return flag; }
struct Edge {
    lint from, to;
    lint cost;
    Edge() {

    }
    Edge(lint u, lint v, lint c) {
        cost = c;
        from = u;
        to = v;
    }
    bool operator<(const Edge& e) const {
        return cost < e.cost;
    }
};
struct WeightedEdge {
    lint to;
    lint cost;
    WeightedEdge(lint v, lint c) {
        to = v;
        cost = c;
    }
    bool operator<(const WeightedEdge& e) const {
        return cost < e.cost;
    }
};
using WeightedGraph = V<V<WeightedEdge>>;
typedef pair<plint, lint> tlint;
typedef pair<ld, ld> pld;
typedef pair<plint, plint> qlint;
typedef pair<lint, string> vstr;
typedef pair<string, string> pstr;
typedef pair<set<lint>, set<lint>> pset;

template<typename flow_t, typename cost_t>
struct Flow {
	const cost_t INF;
	struct edge {
		lint to;
		flow_t cap;
		cost_t cost;
		lint rev;
	};
	vector<vector<edge> > Graph;
	vector<cost_t> potential, min_cost;
	vector<lint> prevv, preve;
	vector<lint> level;
	vector<lint> iter;

	Flow(lint V) :Graph(V), INF(numeric_limits< cost_t >::max()) {}

	void add_edge(lint from, lint to, flow_t cap, cost_t cost = 0) {
		Graph[from].push_back({ to, cap, cost, SZ(Graph[to]) });
		Graph[to].push_back({ from, 0, -cost, SZ(Graph[from]) - 1 });
	}

	void bfs(lint s) {
		lint V = SZ(Graph);
		level.assign(V, -1);
		queue<lint> que;
		que.push(s);
		level[s] = 0;
		while (!que.empty()) {
			lint v = que.front(); que.pop();
			REP(i, SZ(Graph[v])) {
				edge& e = Graph[v][i];
				if (e.cap > 0 && level[e.to] < 0) {
					level[e.to] = level[v] + 1;
					que.push(e.to);
				}
			}
		}
	}

	flow_t dfs(lint v, lint t, flow_t f) {
		if (v == t) return f;
		for (lint& i = iter[v]; i < SZ(Graph[v]); i++) {
			edge& e = Graph[v][i];
			if (e.cap > 0 && level[v] < level[e.to]) {
				flow_t d = dfs(e.to, t, min(f, e.cap));
				if (d > 0) {
					e.cap -= d;
					Graph[e.to][e.rev].cap += d;
					return d;
				}
			}
		}
		return 0;
	}

	flow_t max_flow(lint s, lint t) {
		flow_t flow = 0;
		lint V = SZ(Graph);
		for (;;) {
			bfs(s);
			if (level[t] < 0) return flow;
			iter.assign(V, 0);
			flow_t f;
			while ((f = dfs(s, t, INF)) > 0) {
				flow += f;
			}
		}
	}

	lint min_cost_flow(lint s, lint t, lint f) {
		cost_t res = 0;
		lint V = SZ(Graph);

		potential.assign(V, 0);
		prevv.assign(V, -1);
		preve.assign(V, -1);

		while (f > 0) {
			priority_queue<pair<cost_t, lint>, vector<pair<cost_t, lint> >, greater<pair<cost_t, lint> > > que;
			min_cost.assign(V, INF);
			min_cost[s] = 0;
			que.push({ 0, s });
			while (!que.empty()) {
				pair<cost_t, lint> p = que.top(); que.pop();
				lint v = p.second;
				if (min_cost[v] < p.first) continue;
				REP(i, SZ(Graph[v])) {
					edge& e = Graph[v][i];
					cost_t nextCost = min_cost[v] + e.cost + potential[v] - potential[e.to];
					if (e.cap > 0 && min_cost[e.to] > nextCost) {
						min_cost[e.to] = nextCost;
						prevv[e.to] = v;
						preve[e.to] = i;
						que.push({ min_cost[e.to], e.to });
					}
				}
			}
			if (min_cost[t] == INF) {
				return -1;
			}
			REP(v, V) potential[v] += min_cost[v];

			flow_t addflow = f;
			for (lint v = t; v != s; v = prevv[v]) {
				addflow = min(addflow, Graph[prevv[v]][preve[v]].cap);
			}
			f -= addflow;
			res += addflow * potential[t];
			for (lint v = t; v != s; v = prevv[v]) {
				edge& e = Graph[prevv[v]][preve[v]];
				e.cap -= addflow;
				Graph[v][e.rev].cap += addflow;
			}
		}
		return res;
	}
};

int main() {
	lint N, M;
	cin >> N >> M;
	lint s = N * 2, t = s + 1;
	Flow<lint, lint> g(t + 1);
	REP(i, N) {
		g.add_edge(s, i, 4);
		g.add_edge(i + N, t, 4);
	}
	REP(i, M) {
		lint u, v;
		cin >> u >> v; u--; v--;
		g.add_edge(u, v + N, 4);
	}

	cout << g.max_flow(s, t) - N << endk;
}