#include using namespace std; #pragma GCC optimize("Ofast") #define rep(i,n) for(ll i=0;i=0;i--) #define perl(i,r,l) for(ll i=r-1;i>=l;i--) #define fi first #define se second #define pb push_back #define ins insert #define pqueue(x) priority_queue,greater> #define all(x) (x).begin(),(x).end() #define CST(x) cout<> #define rev(x) reverse(x); using ll=long long; using vl=vector; using vvl=vector>; using pl=pair; using vpl=vector; using vvpl=vector; const ll MOD=1000000007; const ll MOD9=998244353; const int inf=1e9+10; const ll INF=4e18; const ll dy[9]={1,0,-1,0,1,1,-1,-1,0}; const ll dx[9]={0,1,0,-1,1,-1,1,-1,0}; template inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; } template inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; } //公式Dinic; template struct Dinic{ public: Dinic() : _n(0) {} Dinic(int n) : _n(n), g(n) {} int add_edge(int from, int to, Cap cap) { assert(0 <= from && from < _n); assert(0 <= to && to < _n); assert(0 <= cap); int m = int(pos.size()); pos.push_back({from, int(g[from].size())}); g[from].push_back(_edge{to, int(g[to].size()), cap}); g[to].push_back(_edge{from, int(g[from].size()) - 1, 0}); return m; } struct edge { int from, to; Cap cap, flow; }; edge get_edge(int i) { int m = int(pos.size()); assert(0 <= i && i < m); auto _e = g[pos[i].first][pos[i].second]; auto _re = g[_e.to][_e.rev]; return edge{pos[i].first, _e.to, _e.cap + _re.cap, _re.cap}; } std::vector edges() { int m = int(pos.size()); std::vector result; for (int i = 0; i < m; i++) { result.push_back(get_edge(i)); } return result; } void change_edge(int i, Cap new_cap, Cap new_flow) { int m = int(pos.size()); assert(0 <= i && i < m); assert(0 <= new_flow && new_flow <= new_cap); auto& _e = g[pos[i].first][pos[i].second]; auto& _re = g[_e.to][_e.rev]; _e.cap = new_cap - new_flow; _re.cap = new_flow; } Cap flow(int s, int t) { return flow(s, t, std::numeric_limits::max()); } Cap flow(int s, int t, Cap flow_limit) { assert(0 <= s && s < _n); assert(0 <= t && t < _n); std::vector level(_n), iter(_n); queue que; auto bfs = [&]() { std::fill(level.begin(), level.end(), -1); level[s] = 0; while(!que.empty())que.pop(); que.push(s); while (!que.empty()) { int v = que.front(); que.pop(); for (auto e : g[v]) { if (e.cap == 0 || level[e.to] >= 0) continue; level[e.to] = level[v] + 1; if (e.to == t) return; que.push(e.to); } } }; auto dfs = [&](auto self, int v, Cap up) { if (v == s) return up; Cap res = 0; int level_v = level[v]; for (int& i = iter[v]; i < int(g[v].size()); i++) { _edge& e = g[v][i]; if (level_v <= level[e.to] || g[e.to][e.rev].cap == 0) continue; Cap d = self(self, e.to, std::min(up - res, g[e.to][e.rev].cap)); if (d <= 0) continue; g[v][i].cap += d; g[e.to][e.rev].cap -= d; res += d; if (res == up) break; } return res; }; Cap flow = 0; while (flow < flow_limit) { bfs(); if (level[t] == -1) break; std::fill(iter.begin(), iter.end(), 0); while (flow < flow_limit) { Cap f = dfs(dfs, t, flow_limit - flow); if (!f) break; flow += f; } } return flow; } std::vector min_cut(int s) { std::vector visited(_n); queue que; que.push(s); while (!que.empty()) { int p = que.front(); que.pop(); visited[p] = true; for (auto e : g[p]) { if (e.cap && !visited[e.to]) { visited[e.to] = true; que.push(e.to); } } } return visited; } private: int _n; struct _edge { int to, rev; Cap cap; }; std::vector> pos; std::vector> g; }; int main(){ ll n,m;cin >> n >> m; Dinic dn(n*2+2);ll s=n*2,t=s+1; vl a(m),b(m); vl ex(n); rep(i,n)dn.add_edge(s,i,1); rep(i,n)dn.add_edge(i+n,t,1); rep(i,m){ cin >> a[i] >> b[i];a[i]--;b[i]--; dn.add_edge(a[i],b[i]+n,1); dn.add_edge(b[i],a[i]+n,1); ex[a[i]]++;ex[b[i]]++; } ll f=dn.flow(s,t);ll g=f; if(f==n-1){ ll ans=0; rep(i,n){ auto ed=dn.get_edge(i); if(ed.flow==1){ ll d=dn.flow(s,i,1); if(d==0){ dn.flow(t,s,1); dn.flow(s,i,1); g--; } } dn.change_edge(i,0,0); ed=dn.get_edge(i+n); if(ed.flow==1){ ll d=dn.flow(i+n,t,1); if(d==0){ dn.flow(t,s,1); dn.flow(i+n,t,1); g--; } } dn.change_edge(i+n,0,0); g+=dn.flow(s,t); //cout << g << endl; if(g==n-1){ if(ex[i])chmax(ans,n-1); else chmax(ans,n-2); } dn.change_edge(i,1,0); dn.change_edge(i+n,1,0); g+=dn.flow(s,t); } //cout << ans << endl; f=ans; } cout << f*2-n << endl; }