#include using namespace std; typedef long long ll; typedef unsigned long long ull; typedef long double ld; #define FOR(i, a, b) for (int i=a; i<(b); i++) #define range(a) a.begin(), a.end() #define endl "\n" #define Yes() cout << "Yes" << endl #define No() cout << "No" << endl #define MP make_pair using Graph = vector>; const unsigned long long mod = 1e9 + 7; const long long INF = 1LL<<60; const int dx[4]={1,0,-1,0}; const int dy[4]={0,1,0,-1}; void chmin(long long &a, long long b) { if (a > b) a = b; } void chmax(long long &a, long long b) { if (a < b) a = b; } //(xi=f)∨(xj=g)というクローズを足し、これをすべて満たす変数の割当があるかを解きます。(ACL pre H参照) namespace internal { template struct csr { vector start; vector elist; csr(int n, const vector>& edges) : start(n + 1), elist(edges.size()) { for (auto e : edges) { start[e.first + 1]++; } for (int i = 1; i <= n; i++) { start[i] += start[i - 1]; } auto counter = start; for (auto e : edges) { elist[counter[e.first]++] = e.second; } } }; // Reference: // R. Tarjan, // Depth-First Search and Linear Graph Algorithms struct scc_graph { public: scc_graph(int n) : _n(n) {} int num_vertices() { return _n; } void add_edge(int from, int to) { edges.push_back({from, {to}}); } // @return pair of (# of scc, scc id) pair> scc_ids() { auto g = csr(_n, edges); int now_ord = 0, group_num = 0; vector visited, low(_n), ord(_n, -1), ids(_n); visited.reserve(_n); auto dfs = [&](auto self, int v) -> void { low[v] = ord[v] = now_ord++; visited.push_back(v); for (int i = g.start[v]; i < g.start[v + 1]; i++) { auto to = g.elist[i].to; if (ord[to] == -1) { self(self, to); low[v] = min(low[v], low[to]); } else { low[v] = min(low[v], ord[to]); } } if (low[v] == ord[v]) { while (true) { int u = visited.back(); visited.pop_back(); ord[u] = _n; ids[u] = group_num; if (u == v) break; } group_num++; } }; for (int i = 0; i < _n; i++) { if (ord[i] == -1) dfs(dfs, i); } for (auto& x : ids) { x = group_num - 1 - x; } return {group_num, ids}; } vector> scc() { auto ids = scc_ids(); int group_num = ids.first; vector counts(group_num); for (auto x : ids.second) counts[x]++; vector> groups(ids.first); for (int i = 0; i < group_num; i++) { groups[i].reserve(counts[i]); } for (int i = 0; i < _n; i++) { groups[ids.second[i]].push_back(i); } return groups; } private: int _n; struct edge { int to; }; vector> edges; }; } // namespace internal // Reference: // B. Aspvall, M. Plass, and R. Tarjan, // A Linear-Time Algorithm for Testing the Truth of Certain Quantified Boolean // Formulas struct two_sat { public: two_sat() : _n(0), scc(0) {} two_sat(int n) : _n(n), _answer(n), scc(2 * n) {} void add_clause(int i, bool f, int j, bool g) { assert(0 <= i && i < _n); assert(0 <= j && j < _n); scc.add_edge(2 * i + (f ? 0 : 1), 2 * j + (g ? 1 : 0)); scc.add_edge(2 * j + (g ? 0 : 1), 2 * i + (f ? 1 : 0)); } bool satisfiable() { //条件を足す割当が存在するかどうかを判定する auto id = scc.scc_ids().second; for (int i = 0; i < _n; i++) { if (id[2 * i] == id[2 * i + 1]) return false; _answer[i] = id[2 * i] < id[2 * i + 1]; } return true; } vector answer() { return _answer; } //最後に呼んだ satisfiable の、クローズを満たす割当を返す。 private: int _n; vector _answer; internal::scc_graph scc; }; int main(void){ ios::sync_with_stdio(0); cin.tie(0); int N, M; cin >> N >> M; vector L(N), R(N), NL(N), NR(N); FOR(i,0,N){ ll a, b; cin >> a >> b; L.at(i) = a; R.at(i) = b; NR.at(i) = M - L.at(i) - 1; NL.at(i) = M - R.at(i) - 1; } two_sat tf(N); FOR(i,0,N-1){ FOR(j,i+1,N){ if(L.at(i)<=R.at(j)&&R.at(i)>=L.at(j)){ tf.add_clause(i, false, j, false); } if(L.at(i)<=NR.at(j)&&R.at(i)>=NL.at(j)){ tf.add_clause(i, false, j, true); } if(NL.at(i)<=R.at(j)&&NR.at(i)>=L.at(j)){ tf.add_clause(i, true, j, false); } if(NL.at(i)<=NR.at(j)&&NR.at(i)>=NL.at(j)){ tf.add_clause(i, true, j, true); } } } if(tf.satisfiable()) cout << "Yes" << endl; else cout << "No" << endl; return 0; }