#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 UnionFind { explicit UnionFind(const int n) : data(n, -1) {} int root(const int ver) { return data[ver] < 0 ? ver : data[ver] = root(data[ver]); } bool unite(int u, int v) { u = root(u); v = root(v); if (u == v) return false; if (data[u] > data[v]) std::swap(u, v); data[u] += data[v]; data[v] = u; return true; } bool is_same(const int u, const int v) { return root(u) == root(v); } int size(const int ver) { return -data[root(ver)]; } private: std::vector data; }; int main() { int n, m; cin >> n >> m; vector u(m), v(m); REP(i, m) cin >> u[i] >> v[i], --u[i], --v[i]; vector deg(n, 0); UnionFind union_find(n); REP(i, m) { --deg[u[i]]; ++deg[v[i]]; union_find.unite(u[i], v[i]); } vector outdeg(n, 0); REP(i, n) { if (deg[i] > 0) outdeg[union_find.root(i)] += deg[i]; } vector has_edge(n, false); REP(i, m) has_edge[union_find.root(u[i])] = true; int ans = 0; REP(i, n) { if (union_find.root(i) == i && has_edge[i]) { ans += max(outdeg[i], 1); } } cout << ans - 1 << '\n'; return 0; }