#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; using ll = long long; constexpr int INF = 1001001001; // constexpr int mod = 1000000007; constexpr int mod = 998244353; template inline bool chmax(T& x, T y){ if(x < y){ x = y; return true; } return false; } template inline bool chmin(T& x, T y){ if(x > y){ x = y; return true; } return false; } struct StronglyConnectedComponents{ using G = vector>; G graph; G rev; int n; int scc_sz = 0; G scc_graph; vector scc_id; vector vs; vector visited; StronglyConnectedComponents() = default; StronglyConnectedComponents(int V) : n(V) { graph.resize(n); rev.resize(n); scc_id.assign(n, -1); visited.assign(n, false); } StronglyConnectedComponents(G& g) : graph(g), n(g.size()) { rev.resize(n); scc_id.assign(n, -1); visited.assign(n, false); for(int u = 0; u < n; ++u){ for(int v : graph[u]) rev[v].push_back(u); } } void resize(int V){ n = V; graph.resize(n); rev.resize(n); scc_id.assign(n, -1); visited.assign(n, false); } void add_edge(int u, int v){ graph[u].emplace_back(v); rev[v].emplace_back(u); } void dfs(int from){ visited[from] = true; for(int to : graph[from]){ if(!visited[to]) dfs(to); } vs.push_back(from); } void rdfs(int from, int k){ scc_id[from] = k; for(int to : rev[from]){ if(scc_id[to] == -1) rdfs(to, k); } } void build(){ for(int v = 0; v < n; ++v){ if(!visited[v]) dfs(v); } reverse(vs.begin(), vs.end()); for(int v : vs){ if(scc_id[v] == -1) rdfs(v, scc_sz++); } scc_graph.resize(scc_sz); for(int v = 0; v < n; ++v){ scc_graph[scc_id[v]].push_back(v); } return; } int size() { return scc_sz; } vector get_set(int k) { return scc_graph[k]; } int operator[](int v) { return scc_id[v]; } }; struct TwoSAT { StronglyConnectedComponents scc; int n; vector sat; TwoSAT(int V) : n(V) { scc.resize(n * 2); sat.resize(n); } // [false] [true] void add_edge(int i, bool f, int j, bool g){ scc.add_edge(i * 2 + (f ? 0 : 1), j * 2 + (g ? 1 : 0)); scc.add_edge(j * 2 + (g ? 0 : 1), i * 2 + (f ? 1 : 0)); } // sat[v] = true -> v = false // sat[v] = false -> v = true bool satisfiable(){ scc.build(); for(int i = 0; i < n; ++i){ if(scc[i * 2] == scc[i * 2 + 1]) return false; sat[i] = scc[i * 2] < scc[i * 2 + 1]; } return true; } vector get_sat() { return sat; } }; int main(){ ios::sync_with_stdio(false); cin.tie(nullptr); int N, M; cin >> N >> M; vector L(N), R(N), rL(N), rR(N); for(int i = 0; i < N; ++i){ cin >> L[i] >> R[i]; ++R[i]; rL[i] = M - R[i]; rR[i] = M - L[i]; } TwoSAT ts(N); auto check = [](int l1, int r1, int l2, int r2){ return r1 <= l2 || l1 >= r2; }; for(int i = 0; i < N; ++i){ for(int j = 0; j < i; ++j){ if(!check(L[i], R[i], L[j], R[j])){ ts.add_edge(i, false, j, false); } if(!check(L[i], R[i], rL[j], rR[j])){ ts.add_edge(i, false, j, true); } if(!check(rL[i], rR[i], L[j], R[j])){ ts.add_edge(i, true, j, false); } if(!check(rL[i], rR[i], rL[j], rR[j])){ ts.add_edge(i, true, j, true); } } } cout << (ts.satisfiable() ? "YES" : "NO") << '\n'; return 0; }