#include namespace { #pragma GCC diagnostic ignored "-Wunused-function" #include #pragma GCC diagnostic warning "-Wunused-function" using namespace std; using namespace atcoder; #define rep(i,n) for(int i = 0; i < (int)(n); i++) #define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--) #define all(x) begin(x), end(x) #define rall(x) rbegin(x), rend(x) template bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; } template bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; } using ll = long long; using P = pair; using VI = vector; using VVI = vector; using VL = vector; using VVL = vector; // S : group template struct weighted_union_find { public: weighted_union_find() : _n(0) {} explicit weighted_union_find(int n) : _n(n), parent_or_size(n, -1), weight(n, e()) {} int merge(int a, int b, S w) { // W(a->b) = Wa^-1 Wb = w assert(0 <= a && a < _n); assert(0 <= b && b < _n); int x = leader(a), y = leader(b); assert(x != y); if (-parent_or_size[x] < -parent_or_size[y]) { std::swap(x, y); std::swap(a, b); w = inv(w); } // Wa^-1 Wy Wb = w // Wy = Wa w Wb^-1 weight[y] = op(op(weight[a], w), inv(weight[b])); parent_or_size[x] += parent_or_size[y]; parent_or_size[y] = x; return x; } S diff(int a, int b) { // W(a->b) = Wa^-1 Wb int x = leader(a), y = leader(b); assert(x == y); return op(inv(weight[a]), weight[b]); } bool same(int a, int b) { assert(0 <= a && a < _n); assert(0 <= b && b < _n); return leader(a) == leader(b); } int leader(int a) { assert(0 <= a && a < _n); int pre = -1; while (parent_or_size[a] >= 0) { int na = parent_or_size[a]; parent_or_size[a] = pre; pre = a; a = na; } S w = e(); while (pre != -1) { w = op(w, weight[pre]); weight[pre] = w; int npre = parent_or_size[pre]; parent_or_size[pre] = a; pre = npre; } return a; } int size(int a) { assert(0 <= a && a < _n); return -parent_or_size[leader(a)]; } std::vector> groups() { std::vector leader_buf(_n), group_size(_n); for (int i = 0; i < _n; i++) { leader_buf[i] = leader(i); group_size[leader_buf[i]]++; } std::vector> result(_n); for (int i = 0; i < _n; i++) { result[i].reserve(group_size[i]); } for (int i = 0; i < _n; i++) { result[leader_buf[i]].push_back(i); } result.erase( std::remove_if(result.begin(), result.end(), [&](const std::vector& v) { return v.empty(); }), result.end()); return result; } private: int _n; // root node: -1 * component size // otherwise: parent std::vector parent_or_size; std::vector weight; }; ll op(ll x, ll y) { return x + y; } ll e() { return 0; } ll inv(ll x) { return -x; } } int main() { ios::sync_with_stdio(false); cin.tie(0); int n, k; cin >> n >> k; VI r(n); VL x(n); rep(i, n) cin >> r[i] >> x[i]; rep(i, n) { weighted_union_find uf(n + 1); rep(j, n) if (j != i) uf.merge(j, r[j], x[j]); bool ans = [&]() { constexpr long long INF = 1002003004005006007; ll lb = -INF, ub = INF; int L1 = uf.leader(i), L2 = uf.leader(n); assert(L1 != L2); rep(j, n) { if (uf.same(j, j + 1)) { ll d = uf.diff(j, j + 1); if (d < 0 || d > k) return false; } else { int l1 = uf.leader(j), l2 = uf.leader(j + 1); if (l1 == L1) { assert(l2 == L2); ll v = -uf.diff(j, L1) + uf.diff(j+1, L2); chmax(lb, v); chmin(ub, k + v); } else { assert(l1 == L2 && l2 == L1); ll v = uf.diff(j, L2) - uf.diff(j + 1, L1); chmax(lb, v - k); chmin(ub, v); } } } return lb <= ub; }(); cout << (ans ? "Yes\n" : "No\n"); } }