#include using namespace std; #define rep(i, n) for (int i = 0; i < (n); i++) #define per(i, n) for (int i = (n)-1; i >= 0; i--) #define rep2(i, l, r) for (int i = (l); i < (r); i++) #define per2(i, l, r) for (int i = (r)-1; i >= (l); i--) #define each(e, v) for (auto &e : v) #define MM << " " << #define pb push_back #define eb emplace_back #define all(x) begin(x), end(x) #define rall(x) rbegin(x), rend(x) #define sz(x) (int)x.size() using ll = long long; using pii = pair; using pil = pair; using pli = pair; using pll = pair; template using minheap = priority_queue, greater>; template using maxheap = priority_queue; template bool chmax(T &x, const T &y) { return (x < y) ? (x = y, true) : false; } template bool chmin(T &x, const T &y) { return (x > y) ? (x = y, true) : false; } template int flg(T x, int i) { return (x >> i) & 1; } int popcount(int x) { return __builtin_popcount(x); } int popcount(ll x) { return __builtin_popcountll(x); } int topbit(int x) { return (x == 0 ? -1 : 31 - __builtin_clz(x)); } int topbit(ll x) { return (x == 0 ? -1 : 63 - __builtin_clzll(x)); } int botbit(int x) { return (x == 0 ? -1 : __builtin_ctz(x)); } int botbit(ll x) { return (x == 0 ? -1 : __builtin_ctzll(x)); } template void print(const vector &v, T x = 0) { int n = v.size(); for (int i = 0; i < n; i++) cout << v[i] + x << (i == n - 1 ? '\n' : ' '); if (v.empty()) cout << '\n'; } template void printn(const vector &v, T x = 0) { int n = v.size(); for (int i = 0; i < n; i++) cout << v[i] + x << '\n'; } template int lb(const vector &v, T x) { return lower_bound(begin(v), end(v), x) - begin(v); } template int ub(const vector &v, T x) { return upper_bound(begin(v), end(v), x) - begin(v); } template void rearrange(vector &v) { sort(begin(v), end(v)); v.erase(unique(begin(v), end(v)), end(v)); } template vector id_sort(const vector &v, bool greater = false) { int n = v.size(); vector ret(n); iota(begin(ret), end(ret), 0); sort(begin(ret), end(ret), [&](int i, int j) { return greater ? v[i] > v[j] : v[i] < v[j]; }); return ret; } template void reorder(vector &a, const vector &ord) { int n = a.size(); vector b(n); for (int i = 0; i < n; i++) b[i] = a[ord[i]]; swap(a, b); } template T floor(T x, T y) { assert(y != 0); if (y < 0) x = -x, y = -y; return (x >= 0 ? x / y : (x - y + 1) / y); } template T ceil(T x, T y) { assert(y != 0); if (y < 0) x = -x, y = -y; return (x >= 0 ? (x + y - 1) / y : x / y); } template pair operator+(const pair &p, const pair &q) { return make_pair(p.first + q.first, p.second + q.second); } template pair operator-(const pair &p, const pair &q) { return make_pair(p.first - q.first, p.second - q.second); } template istream &operator>>(istream &is, pair &p) { S a; T b; is >> a >> b; p = make_pair(a, b); return is; } template ostream &operator<<(ostream &os, const pair &p) { return os << p.first << ' ' << p.second; } struct io_setup { io_setup() { ios_base::sync_with_stdio(false); cin.tie(NULL); cout << fixed << setprecision(15); } } io_setup; const int inf = (1 << 30) - 1; const ll INF = (1LL << 60) - 1; // const int MOD = 1000000007; const int MOD = 998244353; struct Hopcroft_Karp { vector> es; vector d, match; vector used, used2; const int n, m; Hopcroft_Karp(int n, int m) : es(n), d(n), match(m), used(n), used2(n), n(n), m(m) {} void add_edge(int u, int v) { es[u].push_back(v); } void _bfs() { fill(begin(d), end(d), -1); queue que; for (int i = 0; i < n; i++) { if (!used[i]) { que.push(i); d[i] = 0; } } while (!que.empty()) { int i = que.front(); que.pop(); for (auto &e : es[i]) { int j = match[e]; if (j != -1 && d[j] == -1) { que.push(j); d[j] = d[i] + 1; } } } } bool _dfs(int now) { used2[now] = true; for (auto &e : es[now]) { int u = match[e]; if (u == -1 || (!used2[u] && d[u] == d[now] + 1 && _dfs(u))) { match[e] = now, used[now] = true; return true; } } return false; } int max_matching() { // 右側の i は左側の match[i] とマッチングする fill(begin(match), end(match), -1), fill(begin(used), end(used), false); int ret = 0; while (true) { _bfs(); fill(begin(used2), end(used2), false); int flow = 0; for (int i = 0; i < n; i++) { if (!used[i] && _dfs(i)) flow++; } if (flow == 0) break; ret += flow; } return ret; } }; void solve() { int N, M; cin >> N >> M; Hopcroft_Karp G(N, N); vector deg(N, 0); rep(i, M) { int u, v; cin >> u >> v; u--, v--; G.add_edge(u, v), G.add_edge(v, u); deg[u]++, deg[v]++; } int K = G.max_matching(); if (K != N - 1) { cout << 2 * K - N << '\n'; return; } vector used(N, false); rep(i, N) { if (G.match[i] != -1) used[i] = true, used[G.match[i]] = true; } rep(i, N) { if (!used[i]) { cout << (deg[i] == 0 ? N - 4 : N - 2) << '\n'; return; } } cout << 2 * K - N << '\n'; } int main() { int T = 1; // cin >> T; while (T--) solve(); }