#include using namespace std; #define FOR(i,m,n) for(int i=(m);i<(n);++i) #define REP(i,n) FOR(i,0,n) #define ALL(v) (v).begin(),(v).end() using ll = long long; constexpr int INF = 0x3f3f3f3f; constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL; constexpr double EPS = 1e-8; constexpr int MOD = 998244353; // constexpr int MOD = 1000000007; constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1}; constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1}; constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1}; template inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; } template inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; } struct IOSetup { IOSetup() { std::cin.tie(nullptr); std::ios_base::sync_with_stdio(false); std::cout << fixed << setprecision(20); } } iosetup; struct HopcroftKarp { std::vector match; explicit HopcroftKarp(const int left, const int right) : match(left + right, -1), left(left), t(0), level(left), is_used(left, -1), graph(left) {} void add_edge(const int u, const int v) { graph[u].emplace_back(left + v); } int solve() { int res = 0; while (true) { std::fill(level.begin(), level.end(), -1); std::queue que; for (int i = 0; i < left; ++i) { if (match[i] == -1) { que.emplace(i); level[i] = 0; } } while (!que.empty()) { const int ver = que.front(); que.pop(); for (const int dst : graph[ver]) { if (match[dst] != -1 && level[match[dst]] == -1) { level[match[dst]] = level[ver] + 1; que.emplace(match[dst]); } } } int tmp = 0; for (int i = 0; i < left; ++i) { if (match[i] == -1) { tmp += dfs(i); ++t; } } if (tmp == 0) break; res += tmp; } return res; } private: const int left; int t; std::vector level, is_used; std::vector> graph; bool dfs(const int ver) { is_used[ver] = t; for (const int dst : graph[ver]) { const int m = match[dst]; if (m == -1 || (is_used[m] < t && level[m] == level[ver] + 1 && dfs(m))) { is_used[ver] = t; match[ver] = dst; match[dst] = ver; return true; } } return false; } }; int main() { int n, m; cin >> n >> m; HopcroftKarp hopcroft_karp(n, n); while (m--) { int u, v; cin >> u >> v; --u; --v; hopcroft_karp.add_edge(u, v); hopcroft_karp.add_edge(v, u); } const int ans = hopcroft_karp.solve() * 2 - n; cout << (ans == n - 2 ? n - 4 : ans) << '\n'; return 0; }