#include #include #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() /*-------------------------------------------------*/ struct Edge { int src, dst; Edge(int src, int dst) : src(src), dst(dst) {} }; struct SCC { vector id; // vector > vertices; // vector > comp; SCC(const vector > &graph_) : graph(graph_) { n = graph.size(); rev_graph.resize(n); REP(i, n) for (Edge &e : graph[i]) { rev_graph[e.dst].emplace_back(e.dst, e.src); } used.resize(n); id.resize(n); } int build() { fill(ALL(used), false); order.clear(); fill(ALL(id), -1); // vertices.clear(); // comp.clear(); REP(i, n) { if (!used[i]) dfs(i); } int now = 0; for (int i = n - 1; i >= 0; --i) { if (id[order[i]] == -1) { // vertices.emplace_back(); rev_dfs(order[i], now++); } } // comp.resize(now); // REP(i, n) for (Edge &e : graph[i]) { // if (id[i] != id[e.dst]) comp[id[i]].emplace_back(id[i], id[e.dst], e.cost); // } // REP(i, now) sort(ALL(vertices[i])); return now; } private: int n; vector > graph, rev_graph; vector used; vector order; void dfs(int ver) { used[ver] = true; for (Edge &e : graph[ver]) { if (!used[e.dst]) dfs(e.dst); } order.emplace_back(ver); } void rev_dfs(int ver, int now) { id[ver] = now; // vertices[now].emplace_back(ver); for (Edge &e : rev_graph[ver]) { if (id[e.dst] == -1) rev_dfs(e.dst, now); } } }; struct TwoSat { TwoSat(int n) : n(n) { graph.resize(n * 2); } int negate(int x) { return (n + x) % (n * 2); } void add_if(int x, int y) { graph[x].emplace_back(x, y); } void add_or(int x, int y) { add_if(negate(x), y); add_if(negate(y), x); } void add_nand(int x, int y) { add_or(negate(x), negate(y)); } void set_true(int x) { add_if(negate(x), x); } void set_false(int x) { set_true(negate(x)); } vector build() { SCC scc(graph); scc.build(); vector res(n); REP(i, n) { if (scc.id[i] == scc.id[negate(i)]) return {}; res[i] = scc.id[negate(i)] < scc.id[i]; } return res; } private: int n; vector > graph; }; int main() { cin.tie(nullptr); ios::sync_with_stdio(false); // freopen("input.txt", "r", stdin); int n, m; cin >> n >> m; vector l(n), r(n); REP(i, n) cin >> l[i] >> r[i]; TwoSat ts(n); REP(i, n) REP(j, i) { if (l[i] <= r[j] && l[j] <= r[i]) ts.add_nand(i, j); if (l[i] <= m - l[j] - 1 && m - r[j] - 1 <= r[i]) ts.add_nand(i, ts.negate(j)); if (m - r[i] - 1 <= r[j] && l[j] <= m - l[i] - 1) ts.add_nand(ts.negate(i), j); if (m - r[i] - 1 <= m - l[j] - 1 && m - r[j] - 1 <= m - l[i] - 1) ts.add_nand(ts.negate(i), ts.negate(j)); } cout << (ts.build().empty() ? "NO\n" : "YES\n"); return 0; }