#include using namespace std; using int64 = long long; const int mod = 1e9 + 7; // const int mod = 998244353; const int64 infll = (1LL << 62) - 1; const int inf = (1 << 30) - 1; struct IoSetup { IoSetup() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(10); cerr << fixed << setprecision(10); } } iosetup; template< typename T1, typename T2 > ostream &operator<<(ostream &os, const pair< T1, T2 > &p) { os << p.first << " " << p.second; return os; } template< typename T1, typename T2 > istream &operator>>(istream &is, pair< T1, T2 > &p) { is >> p.first >> p.second; return is; } 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< typename T1, typename T2 > inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); } template< typename T1, typename T2 > inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); } template< typename T = int64 > vector< T > make_v(size_t a) { return vector< T >(a); } template< typename T, typename... Ts > auto make_v(size_t a, Ts... ts) { return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...)); } template< typename T, typename V > typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) { t = v; } template< typename T, typename V > typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) { for(auto &e : t) fill_v(e, v); } template< typename F > struct FixPoint : F { FixPoint(F &&f) : F(forward< F >(f)) {} template< typename... Args > decltype(auto) operator()(Args &&... args) const { return F::operator()(*this, forward< Args >(args)...); } }; template< typename F > inline decltype(auto) MFP(F &&f) { return FixPoint< F >{forward< F >(f)}; } template< typename T = int > struct Edge { int from, to; T cost; int idx; Edge() = default; Edge(int from, int to, T cost = 1, int idx = -1) : from(from), to(to), cost(cost), idx(idx) {} operator int() const { return to; } }; template< typename T = int > struct Graph { vector< vector< Edge< T > > > g; int es; Graph() = default; explicit Graph(int n) : g(n), es(0) {} size_t size() const { return g.size(); } void add_directed_edge(int from, int to, T cost = 1) { g[from].emplace_back(from, to, cost, es++); } void add_edge(int from, int to, T cost = 1) { g[from].emplace_back(from, to, cost, es); g[to].emplace_back(to, from, cost, es++); } void read(int M, int padding = -1, bool weighted = false, bool directed = false) { for(int i = 0; i < M; i++) { int a, b; cin >> a >> b; a += padding; b += padding; T c = T(1); if(weighted) cin >> c; if(directed) add_directed_edge(a, b, c); else add_edge(a, b, c); } } }; template< typename T = int > using Edges = vector< Edge< T > >; /** * @brief Strongly-Connected-Components(強連結成分分解) */ template< typename T = int > struct StronglyConnectedComponents : Graph< T > { public: using Graph< T >::Graph; using Graph< T >::g; vector< int > comp; Graph< T > dag; vector< vector< int > > group; void build() { rg = Graph< T >(g.size()); for(int i = 0; i < g.size(); i++) { for(auto &e : g[i]) { rg.add_directed_edge(e.to, e.from, e.cost); } } comp.assign(g.size(), -1); used.assign(g.size(), 0); for(int i = 0; i < g.size(); i++) dfs(i); reverse(begin(order), end(order)); int ptr = 0; for(int i : order) if(comp[i] == -1) rdfs(i, ptr), ptr++; dag = Graph< T >(ptr); for(int i = 0; i < g.size(); i++) { for(auto &e : g[i]) { int x = comp[e.from], y = comp[e.to]; if(x == y) continue; dag.add_directed_edge(x, y, e.cost); } } group.resize(ptr); for(int i = 0; i < g.size(); i++) { group[comp[i]].emplace_back(i); } } int operator[](int k) const { return comp[k]; } private: vector< int > order, used; Graph< T > rg; void dfs(int idx) { if(exchange(used[idx], true)) return; for(auto &to : g[idx]) dfs(to); order.push_back(idx); } void rdfs(int idx, int cnt) { if(comp[idx] != -1) return; comp[idx] = cnt; for(auto &to : rg.g[idx]) rdfs(to, cnt); } }; int main() { int V, E; cin >> V >> E; StronglyConnectedComponents< int > scc(V); map< pair< int, int >, int > mp; for(int i = 0; i < E; i++) { int a, b, c; cin >> a >> b >> c; --a, --b; if(c == 1) { scc.add_edge(a, b, c); } else { scc.add_directed_edge(a, b, c); } mp[minmax(a, b)]++; } scc.build(); auto group = scc.group; for(auto &p : group) { if(p.size() >= 3) { cout << "Yes" << endl; return 0; } if(p.size() == 2) { if(mp[minmax(p[0], p[1])] >= 2) { cout << "Yes" << endl; return 0; } } } cout << "No" << endl; }